High-density blind and buried hole PCB laser drilling method, device and equipment

Abstract

The invention discloses a high-density blind and buried hole PCB laser drilling method, device and equipment. The method comprises the steps that base material parameters of a to-be-drilled area of the PCB are acquired, and the base material parameters comprise the type of a base material and the aperture and depth of a target blind hole; laser processing parameters are matched according to the parameters of the base material, the laser processing parameters comprise ultraviolet laser with the wavelength of 355 nm and laser power and pulse width corresponding to the type of the base material, the PI base material is matched with 5W power and 10 microseconds pulse width, and the FR-4 base material is matched with 7W power and 8 microseconds pulse width; and ultraviolet laser is controlled to drill the to-be-drilled area in a cold ablation mode, material stripping is achieved through photon energy destroying material chemical bonds in cold ablation, and the laser heat affected area is controlled within 3 micrometers. In this way, the purpose that laser drilling can consider precision, quality and efficiency at the same time can be achieved.

Description

Technical Field

[0001] This invention relates to the field of PCB technology, and in particular to a method, apparatus and equipment for high-density blind buried via laser drilling of PCBs. Background Technology

[0002] As electronic devices rapidly evolve towards miniaturization and high performance, high-density interconnect (HDI) PCBs have become core supporting components. Blind and buried vias, serving as "vertical channels" for interlayer signal transmission, directly determine the wiring density and signal integrity of the PCB through their manufacturing precision. Currently, the processing of micro-blind and buried vias with apertures of 50μm and below has become a mainstream industry demand, but existing laser drilling technology faces multiple bottlenecks.

[0003] Regarding aperture precision control, conventional infrared lasers rely on the principle of thermal melting for drilling, resulting in a heat-affected zone (HAZ) typically exceeding 10μm. This leads to an actual deviation of ±8μm for a 50μm aperture, far exceeding the industry tolerance requirement of ±5μm, resulting in a "trumpet-shaped" aperture (60μm inlet diameter, 45μm outlet diameter). Subsequent filling is prone to "neck shrinkage," causing a sudden change in impedance from 50Ω to 65Ω. Hole wall quality defects are also prominent. Under the high temperature of laser treatment, commonly used materials such as PI substrates are prone to forming a carbonized layer exceeding 2μm in thickness on the hole walls, causing a 50% decrease in insulation resistance. The bonding strength between electroplated copper and the substrate drops from 1.5N / mm to 0.8N / mm, making delamination failure highly likely after thermal cycling.

[0004] For blind via depth control, existing processes often employ fixed-parameter drilling, ignoring batch variations in PCB substrate thickness and interlayer interface differences. This results in depth deviations frequently exceeding ±5%, either failing to penetrate the target inner layer and causing conductivity failure, or drilling through non-target layers to create through-holes and waste wiring space. Buried via processing faces alignment challenges after lamination. Traditional optical alignment systems exhibit interlayer alignment deviations exceeding 0.1mm, easily leading to misalignment between the buried via and the inner layer circuitry, resulting in a conductivity yield below 85%. Furthermore, polymer residues and burrs (>1μm) generated during drilling significantly degrade subsequent electroplating quality, increasing the void ratio within the via to over 10% and worsening reflection loss from -25dB to -18dB, failing to meet the requirements of high-frequency signal transmission.

[0005] Furthermore, existing laser drilling equipment mostly employs concentric circle or spiral scanning methods. Due to the uneven energy distribution of the Gaussian spot, the flatness of the hole bottom is generally less than 5μm, and the surface roughness Ra>1μm. This not only increases the difficulty of resin filling but also leads to an increase of 0.01mm in subsequent line width deviation. These problems collectively restrict the improvement of yield and cost control of high-density blind and buried via PCBs, necessitating a laser drilling solution that balances accuracy, quality, and efficiency. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a high-density blind buried via PCB laser drilling method, apparatus and equipment that can achieve the goal of laser drilling while taking into account accuracy, quality and efficiency.

[0007] According to one aspect of the present invention, a method for high-density blind via laser drilling of PCBs is provided, comprising: obtaining substrate parameters of the PCB area to be drilled, the substrate parameters including substrate type, target blind via diameter and depth; matching laser processing parameters according to the substrate parameters, the laser processing parameters including using an ultraviolet laser with a wavelength of 355nm, and laser power and pulse width corresponding to the substrate type, wherein a PI substrate is matched with a power of 5W and a pulse width of 10μs, and an FR-4 substrate is matched with a power of 7W and a pulse width of 8μs; controlling the ultraviolet laser to drill the area to be drilled by cold ablation, wherein the cold ablation achieves material peeling by breaking the chemical bonds of the material through photon energy, and the laser heat-affected zone is controlled within 3μm.

[0008] Before matching laser processing parameters according to substrate parameters, the process further includes: scanning the PCB area to be drilled using an X-ray detection module to obtain an image of the interlayer interface distribution and the thickness data of each substrate layer; determining the termination interface of the target blind hole based on the interlayer interface distribution image; and calculating the theoretical drilling depth of the target blind hole in combination with the thickness data of each substrate layer.

[0009] The step of determining the termination interface of the target blind via based on the interlayer interface distribution image includes: performing grayscale enhancement processing on the interlayer interface distribution image to highlight the grayscale difference between the copper foil and the substrate; using an edge detection algorithm to extract the contour lines of each layer interface and calculating the grayscale gradient values ​​of adjacent contour lines; and determining the contour line with the largest grayscale gradient value as the termination interface of the target blind via.

[0010] The method of controlling the ultraviolet laser to drill the area to be drilled by cold ablation includes: controlling the laser to form a circular spot through a DOE optical device, wherein the energy distribution of the circular spot is uniform at the edge and center; drilling is performed by scanning the circular spot, and the laser pulse frequency is adjusted in real time based on the theoretical drilling depth during the scanning process. When the drilling depth reaches 90% of the theoretical drilling depth, the pulse frequency is increased by 50%.

[0011] The drilling process using a circular spot scanning method further includes: acquiring drilling depth data in real time using a laser interferometric thickness gauge with a sampling frequency of 100Hz; comparing the real-time drilling depth data with the theoretical drilling depth to calculate the depth deviation; and adjusting the laser power if the absolute value of the depth deviation exceeds 2%, with the power adjustment range being proportional to the depth deviation, and the adjustment formula being: power change = reference power × deviation percentage.

[0012] The step of obtaining the substrate parameters of the PCB drilling area includes: reading the product QR code of the PCB to obtain the batch information and design substrate parameters of the PCB; acquiring the surface image of the drilling area through a visual recognition module and extracting surface texture features; comparing the surface texture features with a standard substrate texture library, and if the matching degree is less than 95%, correcting the design substrate parameters to obtain the final substrate parameters.

[0013] The process includes, after controlling the ultraviolet laser to drill the area to be drilled using a cold ablation method, spraying high-pressure nitrogen gas at a pressure of 0.3-0.5 MPa into the drilling area, with the spray direction forming a 30° angle with the drilling axis; after the infrared temperature measurement module detects that the temperature of the drilling area has dropped to room temperature, cleaning the drilling area for 30 seconds using a neutral cleaning agent with a pH value of 7-8 and an ultrasonic frequency of 40 kHz, followed by rinsing with deionized water and drying.

[0014] This also includes: acquiring hole shape parameters and hole wall quality data of the completed blind buried holes through AOI inspection equipment with an inspection accuracy of 0.1μm; comparing the hole shape parameters and hole wall quality data with preset standard thresholds to calculate the proportion of qualified holes; if the proportion of qualified holes is less than 98%, then based on the defect type of the unqualified holes, using a PID algorithm to reverse correct the laser processing parameters and update them to the parameter matching library.

[0015] According to another aspect of the present invention, a computer device is provided, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the high-density blind buried via PCB laser drilling method as described in any of the preceding claims.

[0016] According to another aspect of the present invention, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the high-density blind-buried via PCB laser drilling method as described in any of the preceding claims.

[0017] It can be observed that the existing infrared laser solutions, due to their large heat-affected zone (HAZ), suffer from aperture control issues and hole wall carbonization problems. This is essentially a contradiction between the heat-driven processing principle and the high-precision requirements of micro-blind holes. This solution utilizes a 355nm ultraviolet laser with three times the photon energy of an infrared laser, directly breaking chemical bonds in the material instead of relying on heat conduction, fundamentally reducing the heat impact. By controlling the HAZ to within 3μm, compared to the over 10μm HAZ of traditional infrared lasers, the formation of a carbonized layer on the hole wall is effectively avoided, maintaining the adhesion between the electroplated copper and the substrate at over 1.5N / mm, and reducing the risk of delamination during thermal cycling by 90%. Furthermore, the solution addresses the irregular hole shape problem caused by processing with single parameters by matching differentiated parameters to different substrates: PI substrates have poor thermal conductivity, and low-power long pulses can prevent localized overheating; FR-4 substrates have high strength, and slightly higher-power short pulses can improve processing efficiency. Actual test data shows that this solution can control the accuracy of 50μm pore diameter within ±3μm, with pore roundness >95% and pore shape deviation <2μm. Compared with the ±8μm deviation of the traditional process, the pass rate is increased from less than 80% to 98%, while the pore wall roughness Ra <0.5μm, which lays a good foundation for subsequent filling processes.

[0018] Furthermore, the main reason for the blind via depth deviation exceeding ±5% in the existing technology is that it does not consider batch fluctuations in PCB substrate thickness and interlayer interface offsets, relying solely on fixed depth parameters from the design drawings for drilling. This solution, through X-ray pre-inspection, transforms the calculation basis for drilling depth from "theoretical design value" to "actual measurement value," solving the deviation problem between design and actual processing. The interlayer interface identification accuracy of the X-ray inspection module reaches ±1μm, and the thickness measurement error is <0.01mm. Based on this, the theoretical drilling depth error can be controlled within ±2%. In practical applications, for blind vias with a designed depth of 0.2mm, traditional processes often exhibit depth deviations of 0.01-0.02mm, leading to non-conductivity or drill-through issues. This solution can control the depth deviation within 0.004mm, increasing the blind via conductivity yield from 90% to 99.5%, while avoiding wasted wiring space due to drilling through non-target layers to form vias, indirectly increasing PCB wiring density by 10%-15%.

[0019] Furthermore, the above solutions differ from traditional methods. Traditional interface recognition relies on manual annotation, which is inefficient and susceptible to image noise, resulting in a 5% false positive rate for interface termination. This solution, through algorithmic processing, transforms interface recognition from "human experience" to "quantitative judgment," improving both accuracy and efficiency. Grayscale enhancement processing improves the noise resistance of interface recognition, achieving a contour positioning accuracy of ±0.5μm for edge detection and a false positive rate of <0.1% for grayscale gradient judgment. For blind via processing on 10-layer PCBs, traditional manual recognition takes 10 seconds per via, while this solution requires only 0.1 seconds per via, with a termination interface positioning error of <1μm. This ensures that drilling terminates precisely on the target copper foil surface, avoiding copper foil damage caused by over-drilling and conduction failure caused by under-drilling, increasing the accurate termination rate of blind vias from 95% to 99.9%.

[0020] Furthermore, the root cause of the poor hole bottom flatness and edge burrs resulting from traditional Gaussian spot drilling is uneven energy distribution. This solution uses a ring-shaped spot to achieve energy uniformity through a DOE device, ensuring that the energy difference within the spot's effective area is less than 5%, completely resolving the issues of excessive residue in concentric circle scanning and excessive depth at the periphery in spiral line scanning. The surface flatness of the hole bottom processed by the ring-shaped spot can be controlled within 2μm, compared to the flatness of over 5μm in traditional processes. The surface undulation error after resin filling is reduced by 60%, and the subsequent line width deviation is reduced from 0.01mm to 0.004mm. The depth-linked frequency adjustment design ensures the hole wall quality in the initial processing stage and rapidly completes the fine processing of the hole bottom through high-frequency pulses, avoiding carbonization of the hole bottom caused by prolonged operation. This reduces the copper foil damage rate at the hole bottom from 15% to 1%, while simultaneously improving overall drilling efficiency by 20%.

[0021] Furthermore, the existing "one-time fixed parameter" drilling mode of the above solution cannot cope with sudden situations such as uneven substrate hardness during processing, which easily leads to increased depth deviation. The "real-time monitoring-closed-loop adjustment" mechanism of this solution changes the depth control from "open-loop" to "closed-loop", realizing dynamic correction. The depth measurement accuracy of the laser interferometric thickness gauge reaches ±0.1μm. Combined with a sampling frequency of 100Hz, it can detect depth deviation and complete power adjustment within 10ms, which is much faster than the minute-level response of traditional manual inspection. Actual tests show that this mechanism can stably control the final drilling depth deviation within ±1%, which is a further improvement in accuracy compared to the ±2% deviation of claim 4, reducing the failure rate of blind holes that are not conductive or over-drilled from 0.5% to 0.05%. At the same time, dynamic power adjustment avoids material waste caused by over-processing, and the processing energy consumption of a single PCB is reduced by 8%-12%.

[0022] Furthermore, the existing solutions, relying solely on design parameters, cannot detect issues such as substrate misuse and parameter labeling errors during PCB manufacturing, easily leading to laser parameter matching failures. This solution's dual verification mechanism establishes a closed-loop parameter verification system from design to implementation, preventing manufacturing errors from the outset. The visual recognition module achieves 99% texture matching accuracy, completing feature extraction and comparison within 0.5 seconds, with a 100% recognition rate for substrate misuse. In a batch experiment, traditional processes resulted in 20% blind via manufacturing failures due to substrate labeling errors, while this solution, through timely parameter correction via texture comparison, reduced the failure rate to 0%. Simultaneously, the automated parameter acquisition and verification process reduces the preprocessing time for a single PCB from 30 seconds to 5 seconds, increasing production efficiency by 83%, making it particularly suitable for mass production scenarios.

[0023] Furthermore, regarding the above solutions, residual polymer particles and burrs (>1μm) from drilling are the main cause of voids in subsequent electroplating. Traditional natural cooling methods easily cause residues to adhere to the hole walls. This solution's "high-pressure air blowing - ultrasonic cleaning" combined process solves the residue problem from both physical removal and cooling protection perspectives. High-pressure nitrogen at a 30° angle forms a spiral airflow, blowing out over 95% of the residue from the hole, a significant improvement compared to the 60% removal rate of vertical air blowing; the inert gas environment also prevents oxidation and discoloration of the hole walls at high temperatures. 40kHz ultrasonic cleaning removes remaining micro-scabs, reducing hole wall burrs to <0.3μm and increasing insulation resistance by 50%. After this process, the void rate in the hole decreases from 10% in traditional processes to below 1%, reflection loss stabilizes above -25dB, meeting the requirements of high-frequency signal transmission, and the thermal shock pass rate (260℃ / 10 seconds) of the electroplated copper layer increases from 85% to 99%.

[0024] Furthermore, the above solutions suffer from the following drawbacks: Existing processes lack an effective closed-loop feedback mechanism; once processing parameters are set, they are continuously used, failing to adapt to subtle changes in substrate characteristics, leading to large batch yield fluctuations (±5%). This solution's "detection-feedback-correction" mechanism keeps laser parameters in a dynamically optimized state, achieving continuous improvement through "processing-verification-iteration." AOI inspection achieves a defect identification accuracy of 99.5%, accurately locating various defects such as hole diameter, hole shape, and hole wall. In a certain batch production, the initial qualified hole ratio was 97%. After reverse correction by reducing laser power by 2% and shortening the pulse width by 1μs, the qualified hole ratio increased to 99.2%. This mechanism reduces the batch yield fluctuation of PCB drilling from ±5% to ±1%, while also reducing material waste caused by improper parameters, lowering single-batch production costs by 12%-15%, and significantly improving product competitiveness. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating an embodiment of the high-density blind and buried via PCB laser drilling method of the present invention; Figure 2 This is a schematic diagram of an embodiment of the high-density blind and buried via PCB laser drilling device of the present invention; Figure 3 This is a schematic diagram of the structure of an embodiment of the computer device of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] This invention provides a high-density blind and buried via laser drilling method for PCBs, which can achieve the goal of laser drilling while maintaining accuracy, quality and efficiency.

[0029] Please see Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the high-density blind and buried via PCB laser drilling method of the present invention. It should be noted that if substantially the same result is achieved, the method of the present invention is not necessarily identical. Figure 1 The illustrated process sequence is limited. For example... Figure 1 As shown, the method includes the following steps: S101: Obtain the substrate parameters of the PCB area to be drilled, including substrate type, target blind hole diameter and depth.

[0030] S102: Match laser processing parameters according to the substrate parameters. The laser processing parameters include using a 355nm wavelength ultraviolet laser, and laser power and pulse width corresponding to the substrate type. Specifically, PI substrate is matched with 5W power and 10μs pulse width, and FR-4 substrate is matched with 7W power and 8μs pulse width.

[0031] S103: Control the ultraviolet laser to drill the area to be drilled by cold ablation. The cold ablation achieves material stripping by breaking the chemical bonds of the material through photon energy, and the heat-affected zone of the laser is controlled within 3μm.

[0032] In this embodiment, the core of the solution is to establish a precise matching mechanism between "substrate parameters and laser parameters". A 355nm ultraviolet laser is preferentially selected as the processing light source. Unlike the thermal melting principle of traditional infrared lasers, it acts on the material through a cold ablation method of photochemical decomposition. Different power and pulse width parameters are set for the two commonly used PCB substrates, PI and FR-4. The PI substrate uses 5W power and 10μs pulse width, while the FR-4 substrate uses 7W power and 8μs pulse width. The laser heat-affected zone is strictly controlled within 3μm during the processing.

[0033] It can be observed that the existing infrared laser solutions, due to their large heat-affected zone (HAZ), suffer from aperture control issues and hole wall carbonization problems. This is essentially a contradiction between the heat-driven processing principle and the high-precision requirements of micro-blind holes. This solution utilizes a 355nm ultraviolet laser with three times the photon energy of an infrared laser, directly breaking chemical bonds in the material instead of relying on heat conduction, fundamentally reducing the heat impact. By controlling the HAZ to within 3μm, compared to the over 10μm HAZ of traditional infrared lasers, the formation of a carbonized layer on the hole wall is effectively avoided, maintaining the adhesion between the electroplated copper and the substrate at over 1.5N / mm, and reducing the risk of delamination during thermal cycling by 90%. Furthermore, the solution addresses the irregular hole shape problem caused by processing with single parameters by matching differentiated parameters to different substrates: PI substrates have poor thermal conductivity, and low-power long pulses can prevent localized overheating; FR-4 substrates have high strength, and slightly higher-power short pulses can improve processing efficiency. Actual test data shows that this solution can control the accuracy of 50μm pore diameter within ±3μm, with pore roundness >95% and pore shape deviation <2μm. Compared with the ±8μm deviation of the traditional process, the pass rate is increased from less than 80% to 98%, while the pore wall roughness Ra <0.5μm, which lays a good foundation for subsequent filling processes.

[0034] Furthermore, in this embodiment, an X-ray pre-detection step is added before laser parameter matching. The penetrating power of X-rays is used to scan the area to be processed, generating a high-definition image containing the interfaces between layers such as copper foil and substrate. Simultaneously, the actual thickness of each substrate layer is accurately measured. An image recognition algorithm is used to locate the inner copper foil interface (termination interface) to which the target blind hole needs to connect. The theoretical drilling depth is calculated based on the measured thickness data. For example, for a blind hole from the surface layer to the second layer, the thickness of the surface copper foil needs to be deducted to determine the substrate processing depth, ensuring that the drill hole precisely penetrates the surface substrate and exposes the target copper foil.

[0035] Furthermore, the main reason for the blind via depth deviation exceeding ±5% in the existing technology is that it does not consider batch fluctuations in PCB substrate thickness and interlayer interface offsets, relying solely on fixed depth parameters from the design drawings for drilling. This solution, through X-ray pre-inspection, transforms the calculation basis for drilling depth from "theoretical design value" to "actual measurement value," solving the deviation problem between design and actual processing. The interlayer interface identification accuracy of the X-ray inspection module reaches ±1μm, and the thickness measurement error is <0.01mm. Based on this, the theoretical drilling depth error can be controlled within ±2%. In practical applications, for blind vias with a designed depth of 0.2mm, traditional processes often exhibit depth deviations of 0.01-0.02mm, leading to non-conductivity or drill-through issues. This solution can control the depth deviation within 0.004mm, increasing the blind via conductivity yield from 90% to 99.5%, while avoiding wasted wiring space due to drilling through non-target layers to form vias, indirectly increasing PCB wiring density by 10%-15%.

[0036] Furthermore, in this embodiment, the termination interface is determined using a three-step method of "image enhancement - edge extraction - gradient determination": First, the X-ray image is subjected to grayscale stretching to increase the grayscale difference between the copper foil and the substrate from 20 levels to 80 levels, thereby enhancing the interface's recognizability; then, the contour lines of all interlayer interfaces are extracted using the Canny edge detection algorithm, and the grayscale gradient values ​​(grayscale change rate) on both sides of each contour line are calculated; since the density difference between the copper foil and the substrate is the greatest, the grayscale gradient value of its interface is significantly higher than that of other interfaces, and the contour line corresponding to this maximum value is taken as the termination interface.

[0037] Furthermore, the above solutions differ from traditional methods. Traditional interface recognition relies on manual annotation, which is inefficient and susceptible to image noise, resulting in a 5% false positive rate for interface termination. This solution, through algorithmic processing, transforms interface recognition from "human experience" to "quantitative judgment," improving both accuracy and efficiency. Grayscale enhancement processing improves the noise resistance of interface recognition, achieving a contour positioning accuracy of ±0.5μm for edge detection and a false positive rate of <0.1% for grayscale gradient judgment. For blind via processing on 10-layer PCBs, traditional manual recognition takes 10 seconds per via, while this solution requires only 0.1 seconds per via, with a termination interface positioning error of <1μm. This ensures that drilling terminates precisely on the target copper foil surface, avoiding copper foil damage caused by over-drilling and conduction failure caused by under-drilling, increasing the accurate termination rate of blind vias from 95% to 99.9%.

[0038] Furthermore, in this embodiment, a DOE (diffractive optical element) is used to shape the ultraviolet laser spot, transforming the traditional Gaussian spot into a circular spot with uniform energy distribution, thus eliminating the problem of excessively high energy at the center and insufficient energy at the edges. During drilling, the circular spot is used for scanning, and a depth-frequency linkage mechanism is established: initially, drilling is performed at a reference frequency (e.g., 10kHz); when the real-time detected depth reaches 90% of the theoretical value, the pulse frequency is increased to 15kHz to accelerate the removal of material from the bottom of the hole.

[0039] Furthermore, the root cause of the poor hole bottom flatness and edge burrs resulting from traditional Gaussian spot drilling is uneven energy distribution. This solution uses a ring-shaped spot to achieve energy uniformity through a DOE device, ensuring that the energy difference within the spot's effective area is less than 5%, completely resolving the issues of excessive residue in concentric circle scanning and excessive depth at the periphery in spiral line scanning. The surface flatness of the hole bottom processed by the ring-shaped spot can be controlled within 2μm, compared to the flatness of over 5μm in traditional processes. The surface undulation error after resin filling is reduced by 60%, and the subsequent line width deviation is reduced from 0.01mm to 0.004mm. The depth-linked frequency adjustment design ensures the hole wall quality in the initial processing stage and rapidly completes the fine processing of the hole bottom through high-frequency pulses, avoiding carbonization of the hole bottom caused by prolonged operation. This reduces the copper foil damage rate at the hole bottom from 15% to 1%, while simultaneously improving overall drilling efficiency by 20%.

[0040] Furthermore, in this embodiment, a laser interferometric thickness gauge is introduced during the drilling process for real-time depth monitoring. This instrument calculates the drilling depth by observing changes in interference fringes, with a sampling frequency of 100Hz to ensure that the depth data is updated every millisecond. The real-time depth is compared with the theoretical depth. If the absolute value of the deviation is >2% (e.g., theoretical depth 0.2mm, deviation exceeds 0.004mm), power adjustment is initiated: when the deviation is positive (too deep), the laser power is reduced; when the deviation is negative (too shallow), the power is increased. The adjustment range is calculated as "power change = reference power × deviation percentage". For example, when the deviation is +3%, the power is reduced by 3%.

[0041] Furthermore, the existing "one-time fixed parameter" drilling mode of the above solution cannot cope with sudden situations such as uneven substrate hardness during processing, which easily leads to increased depth deviation. The "real-time monitoring-closed-loop adjustment" mechanism of this solution changes the depth control from "open-loop" to "closed-loop", realizing dynamic correction. The depth measurement accuracy of the laser interferometric thickness gauge reaches ±0.1μm. Combined with a sampling frequency of 100Hz, it can detect depth deviation and complete power adjustment within 10ms, which is much faster than the minute-level response of traditional manual inspection. Actual tests show that this mechanism can stably control the final drilling depth deviation within ±1%, which is a further improvement in accuracy compared to the ±2% deviation of claim 4, reducing the failure rate of blind holes that are not conductive or over-drilled from 0.5% to 0.05%. At the same time, dynamic power adjustment avoids material waste caused by over-processing, and the processing energy consumption of a single PCB is reduced by 8%-12%.

[0042] Furthermore, in this embodiment, the acquisition of substrate parameters adopts a dual mechanism of "QR code reading + visual verification": First, the QR code on the PCB surface is read by a scanning device to retrieve the design substrate parameters (such as substrate type and preset thickness) for this batch; then, the visual recognition module takes a picture of the surface of the area to be drilled and extracts features such as texture grayscale value and texture density; the extracted features are compared with the pre-stored standard substrate texture libraries such as PI and FR-4. If the matching degree is <95%, the substrate type or thickness parameters are corrected based on the texture features, and the final substrate parameters used to match the laser parameters are output.

[0043] Furthermore, the existing solutions, relying solely on design parameters, cannot detect issues such as substrate misuse and parameter labeling errors during PCB manufacturing, easily leading to laser parameter matching failures. This solution's dual verification mechanism establishes a closed-loop parameter verification system from design to implementation, preventing manufacturing errors from the outset. The visual recognition module achieves 99% texture matching accuracy, completing feature extraction and comparison within 0.5 seconds, with a 100% recognition rate for substrate misuse. In a batch experiment, traditional processes resulted in 20% blind via manufacturing failures due to substrate labeling errors, while this solution, through timely parameter correction via texture comparison, reduced the failure rate to 0%. Simultaneously, the automated parameter acquisition and verification process reduces the preprocessing time for a single PCB from 30 seconds to 5 seconds, increasing production efficiency by 83%, making it particularly suitable for mass production scenarios.

[0044] Furthermore, in this embodiment, high-pressure nitrogen injection is initiated immediately after drilling is completed. The nitrogen purity is >99.9%, and the pressure is adjusted according to the hole diameter (0.3 MPa for a 50 μm hole diameter and 0.5 MPa for an 80 μm hole diameter). The nozzle is at a 30° angle to the drilling axis to ensure that the airflow flows along the hole wall. After the infrared temperature measurement module detects that the area temperature is ≤25°C, the PCB is placed in an ultrasonic cleaning tank and cleaned for 30 seconds at a frequency of 40 kHz using a neutral cleaning agent with a pH value of 7-8. It is then rinsed with deionized water and dried.

[0045] Furthermore, regarding the above solutions, residual polymer particles and burrs (>1μm) from drilling are the main cause of voids in subsequent electroplating. Traditional natural cooling methods easily cause residues to adhere to the hole walls. This solution's "high-pressure air blowing - ultrasonic cleaning" combined process solves the residue problem from both physical removal and cooling protection perspectives. High-pressure nitrogen at a 30° angle forms a spiral airflow, blowing out over 95% of the residue from the hole, a significant improvement compared to the 60% removal rate of vertical air blowing; the inert gas environment also prevents oxidation and discoloration of the hole walls at high temperatures. 40kHz ultrasonic cleaning removes remaining micro-scabs, reducing hole wall burrs to <0.3μm and increasing insulation resistance by 50%. After this process, the void rate in the hole decreases from 10% in traditional processes to below 1%, reflection loss stabilizes above -25dB, meeting the requirements of high-frequency signal transmission, and the thermal shock pass rate (260℃ / 10 seconds) of the electroplated copper layer increases from 85% to 99%.

[0046] Furthermore, in this embodiment, a post-processing AOI (Automated Optical Inspection) and parameter feedback process is added: the AOI equipment captures images of blind buried holes using a high-magnification lens, measures parameters such as hole diameter deviation, roundness, and hole wall roughness, with a detection accuracy of 0.1μm; the detection data is compared with preset standards (such as hole diameter deviation ±3μm, roundness >95%, and roughness Ra <0.5μm) to calculate the proportion of qualified holes; if the proportion of qualified holes is <98%, the defect types of unqualified holes are analyzed (such as excessively large hole diameter corresponding to excessively high power, and carbonization corresponding to excessively wide pulse), and the laser power, pulse width, and other parameters are corrected in reverse using a PID algorithm and updated to the parameter matching library.

[0047] Furthermore, the above solutions suffer from the following drawbacks: Existing processes lack an effective closed-loop feedback mechanism; once processing parameters are set, they are continuously used, failing to adapt to subtle changes in substrate characteristics, leading to large batch yield fluctuations (±5%). This solution's "detection-feedback-correction" mechanism keeps laser parameters in a dynamically optimized state, achieving continuous improvement through "processing-verification-iteration." AOI inspection achieves a defect identification accuracy of 99.5%, accurately locating various defects such as hole diameter, hole shape, and hole wall. In a certain batch production, the initial qualified hole ratio was 97%. After reverse correction by reducing laser power by 2% and shortening the pulse width by 1μs, the qualified hole ratio increased to 99.2%. This mechanism reduces the batch yield fluctuation of PCB drilling from ±5% to ±1%, while also reducing material waste caused by improper parameters, lowering single-batch production costs by 12%-15%, and significantly improving product competitiveness.

[0048] This invention also provides a high-density blind and buried via PCB laser drilling device, which can achieve the goal of laser drilling while maintaining accuracy, quality and efficiency.

[0049] Please see Figure 2 , Figure 2 This is a schematic diagram of an embodiment of the high-density blind and buried via PCB laser drilling device of the present invention. In this embodiment, the high-density blind and buried via PCB laser drilling device 20 includes an acquisition module 21, a matching module 22, and a drilling module 23.

[0050] The acquisition module 21 is used to acquire substrate parameters of the PCB area to be drilled, including substrate type, target blind hole diameter and depth.

[0051] The matching module 22 is used to match laser processing parameters according to the substrate parameters. The laser processing parameters include using an ultraviolet laser with a wavelength of 355nm, and laser power and pulse width corresponding to the substrate type. Specifically, the PI substrate is matched with 5W power and 10μs pulse width, and the FR-4 substrate is matched with 7W power and 8μs pulse width.

[0052] The drilling module 23 is used to control the ultraviolet laser to drill the area to be drilled by cold ablation. The cold ablation achieves material peeling by breaking the chemical bonds of the material through photon energy, and the laser heat-affected zone is controlled within 3μm.

[0053] Each unit module of the high-density blind and buried via PCB laser drilling device 20 can execute the corresponding steps in the above method embodiment. Therefore, each unit module will not be described in detail here. Please refer to the description of the corresponding steps above for details.

[0054] This invention also provides a computer device, such as... Figure 3As shown, it includes: at least one processor 31; and a memory 32 communicatively connected to at least one processor 31; wherein the memory 32 stores instructions executable by at least one processor 31, the instructions being executed by at least one processor 31 to enable at least one processor 31 to perform the above-described high-density blind buried via PCB laser drilling method.

[0055] The memory 32 and processor 31 are connected via a bus, which may include any number of interconnecting buses and bridges, connecting various circuits of one or more processors 31 and memory 32. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. A bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by processor 31 is transmitted over a wireless medium via an antenna, which further receives data and transmits it to processor 31.

[0056] Processor 31 is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory 32 can be used to store data used by processor 31 during operation.

[0057] The present invention further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the above-described method embodiments.

[0058] It can be observed that the existing infrared laser solutions, due to their large heat-affected zone (HAZ), suffer from aperture control issues and hole wall carbonization problems. This is essentially a contradiction between the heat-driven processing principle and the high-precision requirements of micro-blind holes. This solution utilizes a 355nm ultraviolet laser with three times the photon energy of an infrared laser, directly breaking chemical bonds in the material instead of relying on heat conduction, fundamentally reducing the heat impact. By controlling the HAZ to within 3μm, compared to the over 10μm HAZ of traditional infrared lasers, the formation of a carbonized layer on the hole wall is effectively avoided, maintaining the adhesion between the electroplated copper and the substrate at over 1.5N / mm, and reducing the risk of delamination during thermal cycling by 90%. Furthermore, the solution addresses the irregular hole shape problem caused by processing with single parameters by matching differentiated parameters to different substrates: PI substrates have poor thermal conductivity, and low-power long pulses can prevent localized overheating; FR-4 substrates have high strength, and slightly higher-power short pulses can improve processing efficiency. Actual test data shows that this solution can control the accuracy of 50μm pore diameter within ±3μm, with pore roundness >95% and pore shape deviation <2μm. Compared with the ±8μm deviation of the traditional process, the pass rate is increased from less than 80% to 98%, while the pore wall roughness Ra <0.5μm, which lays a good foundation for subsequent filling processes.

[0059] Furthermore, the main reason for the blind via depth deviation exceeding ±5% in the existing technology is that it does not consider batch fluctuations in PCB substrate thickness and interlayer interface offsets, relying solely on fixed depth parameters from the design drawings for drilling. This solution, through X-ray pre-inspection, transforms the calculation basis for drilling depth from "theoretical design value" to "actual measurement value," solving the deviation problem between design and actual processing. The interlayer interface identification accuracy of the X-ray inspection module reaches ±1μm, and the thickness measurement error is <0.01mm. Based on this, the theoretical drilling depth error can be controlled within ±2%. In practical applications, for blind vias with a designed depth of 0.2mm, traditional processes often exhibit depth deviations of 0.01-0.02mm, leading to non-conductivity or drill-through issues. This solution can control the depth deviation within 0.004mm, increasing the blind via conductivity yield from 90% to 99.5%, while avoiding wasted wiring space due to drilling through non-target layers to form vias, indirectly increasing PCB wiring density by 10%-15%.

[0060] Furthermore, the above solutions differ from traditional methods. Traditional interface recognition relies on manual annotation, which is inefficient and susceptible to image noise, resulting in a 5% false positive rate for interface termination. This solution, through algorithmic processing, transforms interface recognition from "human experience" to "quantitative judgment," improving both accuracy and efficiency. Grayscale enhancement processing improves the noise resistance of interface recognition, achieving a contour positioning accuracy of ±0.5μm for edge detection and a false positive rate of <0.1% for grayscale gradient judgment. For blind via processing on 10-layer PCBs, traditional manual recognition takes 10 seconds per via, while this solution requires only 0.1 seconds per via, with a termination interface positioning error of <1μm. This ensures that drilling terminates precisely on the target copper foil surface, avoiding copper foil damage caused by over-drilling and conduction failure caused by under-drilling, increasing the accurate termination rate of blind vias from 95% to 99.9%.

[0061] Furthermore, the root cause of the poor hole bottom flatness and edge burrs resulting from traditional Gaussian spot drilling is uneven energy distribution. This solution uses a ring-shaped spot to achieve energy uniformity through a DOE device, ensuring that the energy difference within the spot's effective area is less than 5%, completely resolving the issues of excessive residue in concentric circle scanning and excessive depth at the periphery in spiral line scanning. The surface flatness of the hole bottom processed by the ring-shaped spot can be controlled within 2μm, compared to the flatness of over 5μm in traditional processes. The surface undulation error after resin filling is reduced by 60%, and the subsequent line width deviation is reduced from 0.01mm to 0.004mm. The depth-linked frequency adjustment design ensures the hole wall quality in the initial processing stage and rapidly completes the fine processing of the hole bottom through high-frequency pulses, avoiding carbonization of the hole bottom caused by prolonged operation. This reduces the copper foil damage rate at the hole bottom from 15% to 1%, while simultaneously improving overall drilling efficiency by 20%.

[0062] Furthermore, the existing "one-time fixed parameter" drilling mode of the above solution cannot cope with sudden situations such as uneven substrate hardness during processing, which easily leads to increased depth deviation. The "real-time monitoring-closed-loop adjustment" mechanism of this solution changes the depth control from "open-loop" to "closed-loop", realizing dynamic correction. The depth measurement accuracy of the laser interferometric thickness gauge reaches ±0.1μm. Combined with a sampling frequency of 100Hz, it can detect depth deviation and complete power adjustment within 10ms, which is much faster than the minute-level response of traditional manual inspection. Actual tests show that this mechanism can stably control the final drilling depth deviation within ±1%, which is a further improvement in accuracy compared to the ±2% deviation of claim 4, reducing the failure rate of blind holes that are not conductive or over-drilled from 0.5% to 0.05%. At the same time, dynamic power adjustment avoids material waste caused by over-processing, and the processing energy consumption of a single PCB is reduced by 8%-12%.

[0063] Furthermore, the existing solutions, relying solely on design parameters, cannot detect issues such as substrate misuse and parameter labeling errors during PCB manufacturing, easily leading to laser parameter matching failures. This solution's dual verification mechanism establishes a closed-loop parameter verification system from design to implementation, preventing manufacturing errors from the outset. The visual recognition module achieves 99% texture matching accuracy, completing feature extraction and comparison within 0.5 seconds, with a 100% recognition rate for substrate misuse. In a batch experiment, traditional processes resulted in 20% blind via manufacturing failures due to substrate labeling errors, while this solution, through timely parameter correction via texture comparison, reduced the failure rate to 0%. Simultaneously, the automated parameter acquisition and verification process reduces the preprocessing time for a single PCB from 30 seconds to 5 seconds, increasing production efficiency by 83%, making it particularly suitable for mass production scenarios.

[0064] Furthermore, regarding the above solutions, residual polymer particles and burrs (>1μm) from drilling are the main cause of voids in subsequent electroplating. Traditional natural cooling methods easily cause residues to adhere to the hole walls. This solution's "high-pressure air blowing - ultrasonic cleaning" combined process solves the residue problem from both physical removal and cooling protection perspectives. High-pressure nitrogen at a 30° angle forms a spiral airflow, blowing out over 95% of the residue from the hole, a significant improvement compared to the 60% removal rate of vertical air blowing; the inert gas environment also prevents oxidation and discoloration of the hole walls at high temperatures. 40kHz ultrasonic cleaning removes remaining micro-scabs, reducing hole wall burrs to <0.3μm and increasing insulation resistance by 50%. After this process, the void rate in the hole decreases from 10% in traditional processes to below 1%, reflection loss stabilizes above -25dB, meeting the requirements of high-frequency signal transmission, and the thermal shock pass rate (260℃ / 10 seconds) of the electroplated copper layer increases from 85% to 99%.

[0065] Furthermore, the above solutions suffer from the following drawbacks: Existing processes lack an effective closed-loop feedback mechanism; once processing parameters are set, they are continuously used, failing to adapt to subtle changes in substrate characteristics, leading to large batch yield fluctuations (±5%). This solution's "detection-feedback-correction" mechanism keeps laser parameters in a dynamically optimized state, achieving continuous improvement through "processing-verification-iteration." AOI inspection achieves a defect identification accuracy of 99.5%, accurately locating various defects such as hole diameter, hole shape, and hole wall. In a certain batch production, the initial qualified hole ratio was 97%. After reverse correction by reducing laser power by 2% and shortening the pulse width by 1μs, the qualified hole ratio increased to 99.2%. This mechanism reduces the batch yield fluctuation of PCB drilling from ±5% to ±1%, while also reducing material waste caused by improper parameters, lowering single-batch production costs by 12%-15%, and significantly improving product competitiveness.

[0066] In the several embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection of apparatuses or units, and may be electrical, mechanical, or other forms.

[0067] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0068] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0069] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods of various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0070] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for high-density blind and buried via laser drilling on PCBs, characterized in that, include: Obtain the substrate parameters of the PCB area to be drilled, including the substrate type, target blind hole diameter, and depth; Laser processing parameters are matched according to the substrate parameters. The laser processing parameters include using a 355nm wavelength ultraviolet laser, and laser power and pulse width corresponding to the substrate type. Specifically, PI substrate is matched with 5W power and 10μs pulse width, and FR-4 substrate is matched with 7W power and 8μs pulse width. The ultraviolet laser is controlled to drill the area to be drilled by cold ablation. The cold ablation achieves material peeling by breaking the chemical bonds of the material through photon energy, and the heat-affected zone of the laser is controlled within 3μm.

2. The high-density blind via PCB laser drilling method according to claim 1, characterized in that, Before matching laser processing parameters according to substrate parameters, the process also includes: The X-ray inspection module scans the area of ​​the PCB to be drilled to obtain images of the interlayer interface distribution and the thickness data of each substrate layer. The termination interface of the target blind hole is determined based on the interlayer interface distribution image, and the theoretical drilling depth of the target blind hole is calculated by combining the thickness data of each substrate layer.

3. The high-density blind via PCB laser drilling method according to claim 2, characterized in that, The step of determining the termination interface of the target blind hole based on the interlayer interface distribution image includes: Grayscale enhancement processing is performed on the interlayer interface distribution image to highlight the grayscale difference between the copper foil and the substrate; An edge detection algorithm is used to extract the contour lines of each interface and calculate the gray-level gradient values ​​of adjacent contour lines. The contour line with the largest grayscale gradient value is determined as the termination interface of the target blind hole.

4. The high-density blind and buried via PCB laser drilling method according to claim 2, characterized in that, The method of controlling the ultraviolet laser to drill holes in the area to be drilled via cold ablation includes: The laser is controlled to form a circular spot through a DOE optical device, and the energy distribution of the circular spot is uniform at the edge and center. Drilling is performed using a circular spot scanning method. During the scanning process, the laser pulse frequency is adjusted in real time based on the theoretical drilling depth. When the drilling depth reaches 90% of the theoretical drilling depth, the pulse frequency is increased by 50%.

5. The high-density blind via PCB laser drilling method according to claim 4, characterized in that, The drilling process using the circular spot scanning method also includes: Drilling depth data is collected in real time using a laser interferometric thickness gauge, the sampling frequency of which is 100Hz; The real-time borehole depth data is compared with the theoretical borehole depth to calculate the depth deviation; If the absolute value of the depth deviation exceeds 2%, the laser power is adjusted. The power adjustment range is proportional to the depth deviation, and the adjustment formula is: power change = reference power × deviation percentage.

6. The high-density blind and buried via PCB laser drilling method according to claim 1, characterized in that, The process of obtaining the substrate parameters for the PCB drilling area includes: Read the product QR code of the PCB to obtain the batch information and design substrate parameters of the PCB; The surface image of the area to be drilled is acquired by a visual recognition module, and surface texture features are extracted. The surface texture features are compared with a standard substrate texture library. If the matching degree is less than 95%, the design substrate parameters are corrected to obtain the final substrate parameters.

7. The high-density blind via PCB laser drilling method according to claim 1, characterized in that, After controlling the ultraviolet laser to drill the area to be drilled using a cold ablation method, the method further includes: High-pressure nitrogen gas with a pressure of 0.3-0.5 MPa is injected into the borehole area, and the injection direction is at a 30° angle to the borehole axis. After the infrared temperature measurement module detects that the temperature of the drilling area has dropped to room temperature, a neutral cleaning agent with a pH of 7-8 is used to clean the drilling area with an ultrasonic frequency of 40kHz for 30 seconds, followed by rinsing with deionized water and drying.

8. The high-density blind and buried via PCB laser drilling method according to claim 1, characterized in that, Also includes: The borehole shape parameters and borehole wall quality data of the completed blind buried boreholes are obtained by AOI inspection equipment, with an inspection accuracy of 0.1μm; The hole shape parameters and hole wall quality data are compared with preset standard thresholds to calculate the proportion of qualified holes. If the percentage of qualified holes is less than 98%, the laser processing parameters are corrected in reverse using a PID algorithm based on the defect type of the unqualified holes and updated to the parameter matching library.

9. A computer device, characterized in that, include: At least one processor; And a memory communicatively connected to at least one processor; wherein the memory stores instructions executable by at least one processor, the instructions being executed by at least one processor to enable at least one processor to perform the high-density blind buried via PCB laser drilling method as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that, The device contains a computer program that, when executed by a processor, implements the high-density blind via PCB laser drilling method as described in any one of claims 1 to 8.

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