Rigid-flex circuit board slotting process based on laser depth control technology

Abstract

The invention discloses a rigid-flex circuit board slotting process based on a laser depth control technology. The rigid-flex circuit board slotting process comprises the steps that the surface of a rigid layer of a rigid-flex circuit board is pretreated, and a laser sensitive layer is sprayed; cNC depth-controlled milling is adopted to form a grooved rough blank structure on the surface of the pretreated rigid layer; positioning laser is used for scanning, a three-dimensional model is established through collected reflected signals, then layered depth-controlled ablation is conducted, second-power laser is sequentially adopted for fine cutting, third-power laser is sequentially adopted for depth calibration, and a groove body structure is formed; cleaning an interface, scanning a groove bottom area and synchronously introducing low-temperature gas; performing morphology repairing treatment, and generating a periodic micro-nano structure on the groove wall by adopting short pulse laser to form a stress concentration resistant surface; depositing an insulating medium layer, and forming a continuous packaging protection layer on the groove wall and the bottom through a vacuum coating process; the high-precision depth-controlled slotting of the rigid-flex circuit board is realized, and meanwhile, the ultra-low thermal damage and anti-fatigue structure and long-acting environmental stability are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to a slotting process for a hard-and-soft combined circuit board based on laser depth control technology. Background Art

[0002] As key components for the miniaturization and functional integration of 3C electronic products, rigid-flexible circuit boards are widely used in consumer electronics such as smartphones, foldable devices, and smartwatches. For example, the camera module of a smart device requires integrating a rigid image sensor mounting area and a flexible circuit transmission channel within a circuit board with a thickness of ≤0.8mm. High-precision grooving is required to achieve stress relief and signal shielding in the rigid-flexible transition area. Traditional machining processes are prone to tearing the flexible layer due to their lack of precision. Laser-controlled depth grooving has become the core process for achieving micron-level groove processing, directly impacting product lightweighting and reliability.

[0003] The current 3C electronics field mainly uses a single laser to groove rigid-flex boards, removing the rigid layer material layer by layer by fixing the laser parameters. However, due to the significant difference in thermodynamic properties between the rigid layer and the flexible layer in 3C products, a single laser energy parameter is prone to two types of failure problems: (1) In the high-energy mode, the heat accumulation generated during the ablation of the rigid layer is transferred to the flexible layer through the interface, causing pyrolytic carbonization of the polyimide substrate and thermal damage to the flexible layer. (2) In low-energy mode, the rigid layer is not cut thoroughly, leaving unburned glass fibers, which leads to delamination and cracking at the edge of the slot during the subsequent pressing process, seriously affecting the yield rate of the camera focus module. This contradiction has become a core technical bottleneck restricting the high-density and reliability improvement of 3C electronic products.

[0004] In view of this, it is necessary to improve the existing circuit board laser grooving technology to solve the technical problems of uncontrolled ablation depth, interface thermal damage and insufficient groove structure life caused by differences in material thermal response. Summary of the Invention

[0005] The purpose of the present invention is to provide a grooving process for a rigid-flexible circuit board based on laser depth control technology to solve the above technical problems.

[0006] To achieve this object, the present invention adopts the following technical solutions: A grooving process for a rigid-flexible circuit board based on laser depth control technology includes the following steps: Pre-treating the surface of the rigid layer of the rigid-flex circuit board by mechanically grinding to reduce the surface roughness and spraying a laser-sensitive layer on the surface. The laser-sensitive layer contains an optical material for wavelength-selective absorption. CNC controlled deep milling is used to form a slotted rough structure on the surface of the pre-treated rigid layer; Performing laser scanning modeling on the slotted blank structure, and establishing a three-dimensional model including optical material density and thickness distribution through the collected reflection signals; Laser finishing is performed based on the three-dimensional corrected model, and a second power laser is used for fine cutting and a third power laser is used for depth calibration in sequence to form a stepped transition groove structure; The processed groove interface is cleaned, the ultraviolet laser is switched to scan the groove bottom area and low-temperature gas is introduced simultaneously to remove residual adhesive and inhibit the expansion of the heat-affected zone.

[0007] Optionally, the process includes cleaning the processed groove interface, switching the ultraviolet laser to scan the groove bottom area and simultaneously introducing low-temperature gas to remove residual adhesive and inhibit the expansion of the heat-affected zone, and then further comprising: The cleaned groove surface is repaired by using a short-pulse laser to generate a periodic micro-nano structure on the groove wall to form a surface that resists stress concentration. An insulating dielectric layer is deposited on the surface of the repaired slot body, and a continuous encapsulation protective layer is formed on the slot wall and bottom through a vacuum coating process.

[0008] Optionally, the laser sensitive layer is specifically composed of: 30%~45% wavelength selective absorber, 50%~65% thermal stability binder and 5%~8% dispersing agent; The thickness of the laser sensitive layer is 8-15 μm, the absorption rate of the laser with a wavelength of 1064 nm is ≥90%, and the reflectivity of the laser with a wavelength of 355 nm is ≥85%.

[0009] Optionally, the wavelength selective absorber is composed of carbon nanotubes and iron oxide composite nanoparticles, wherein the mass ratio of carbon nanotubes to iron oxide is 1:2 to 1:4; the thermal stability binder is selected as silicone modified epoxy resin; and the dispersing aid is selected as polyether modified silicone.

[0010] Optionally, laser scanning modeling is performed on the slotted blank structure, and a three-dimensional model including density and thickness distribution of optical materials is established through the collected reflection signals, specifically including: Planning a laser scanning path, generating a scanning trajectory according to the preset boundary coordinates of the slotted blank structure, setting the line spacing of the scanning trajectory to 1 / 3 of the laser spot diameter, and presetting a dynamic focus compensation interval of 0.05-0.2 mm along the Z-axis direction; Perform multispectral reflection signal acquisition, using a 532nm green laser with a pulse power of 8-12W to illuminate the surface of the rigid layer along the scanning trajectory, synchronously receiving the 532nm fundamental frequency light intensity signal and the 1064nm second harmonic signal in the reflected light, and establishing a material absorption characteristic distribution map; Implement interferometric measurement modeling, guide part of the reflected light into the interferometer through a beam splitter prism, calculate the surface height change based on the displacement of the interference fringes, and generate initial 3D profile data; The multimodal data is integrated to establish a physical field model. The material absorption characteristic distribution map and 3D contour data are input into the finite element algorithm. Combined with the dielectric constant gradient parameters of the laser-sensitive layer, the material density distribution inside the rigid layer and the adhesive interface thickness are inversely calculated to establish a 3D model. The energy absorption threshold of the slotted area in the three-dimensional model is dynamically calibrated according to the density-thickness coupling relationship, and a digital processing map including ablation priority marks is generated to optimize the three-dimensional model.

[0011] Optionally, the laser finishing based on the three-dimensional corrected model, sequentially using a second power laser for fine cutting and a third power laser for depth calibration to form a stepped transition trough structure, specifically includes the following steps: Analyze the ablation priority mark in the three-dimensional model and divide the slotting area into a core ablation area and an edge transition area, where the core ablation area is set as the first power laser action area and the edge transition area is set as the second power laser action area; Perform the first power laser rough cutting, using an infrared laser with a peak power of 30-50W to scan along the core area at a scanning speed of 400-600mm / s to complete the depth control of the first depth of the slotted area, and synchronously trigger the plasma spectrum monitoring module to determine the residual amount of glass fiber in real time; Adaptive energy gradient regulation is implemented, and the second power laser parameters are dynamically adjusted according to the residual data. In the edge transition zone, 18-25W power is used and oblique scanning is performed at a speed of 800-1000mm / s to form a groove structure with a groove wall taper angle of 5-15°. Using a third-power laser with an annular spot, the depth calibration of spiral finishing is performed along the groove bottom contour at a speed of 1200-1500mm / s. The depth deviation is fed back and compensated in real time through the confocal sensor. A cross-layer thermal stress equalization process is performed, a preset delay period is inserted after each power cutting is completed, and a high-frequency pulse is applied to perform micro-impact on the cutting surface to eliminate the interlayer stress concentration of the trough structure.

[0012] Optionally, the annular light spot is set to have an outer ring diameter of 80-120 μm and an inner ring diameter of 30-50 μm.

[0013] Optionally, the process of cleaning the processed groove interface, switching the ultraviolet laser to scan the groove bottom area and simultaneously introducing low-temperature gas to remove residual adhesive and inhibit the expansion of the heat-affected zone specifically includes the following steps: The low-temperature gas synergy parameters are set, and the nitrogen jet temperature and flow rate are controlled according to the depth gradient distribution of the groove body. An axial temperature gradient field is formed at the bottom of the groove, which causes differential thermal strain in the adhesive and polyimide layer. Perform multi-mode laser cleaning, using a 355nm UV laser with a frequency of 20-30kHz and a power of 5-8W for spiral scanning. In the initial stage, a Gaussian spot is used to remove loose adhesive on the surface, and in the later stage, a flat-top spot is used to remove interface-bound residues. Implement dynamic energy coupling regulation, based on the real-time infrared thermal imaging data feedback of the temperature field changes at the bottom of the tank, and dynamically adjust the laser duty cycle and gas flow rate to ensure that the local temperature rise is always lower than the glass transition temperature of the polyimide; By online detection of the characteristic peaks at the bottom of the groove, cleaning is terminated when the residual adhesive signal intensity is less than the preset threshold, and the heat-affected zone width data is simultaneously recorded for process iterative optimization.

[0014] Optionally, the morphology repair process is performed on the cleaned groove surface, and a short pulse laser is used to generate a periodic micro-nano structure on the groove wall to form a stress concentration resistant surface, which specifically includes the following steps: Pre-treat the contaminants on the tank wall surface by using laser to perform full-area scanning to remove the nano-scale oxide layer and activate the surface chemical bond activity; A dual-beam interference processing field is constructed to split the short-pulse laser into two coherent beams, forming interference fringes with adjustable spatial period on the groove wall surface. The phase difference is controlled by a piezoelectric ceramic translation stage to induce plasmon-enhanced ablation on the surface. Gradient energy etching is performed, and the laser flux is adjusted in three sections along the depth direction of the groove body. A parallel groove structure is generated in the groove area, a scale-like stacked structure is generated in the middle of the groove, and a radial corrugated structure is generated at the bottom of the groove, thereby generating a periodic micro-nano structure on the groove wall. Perform dynamic stress compensation, apply 40-60kHz ultrasonic vibration during laser processing, dynamically adjust the laser repetition frequency and scanning speed, reduce the residual stress of the periodic micro-nano structure to the qualified threshold, and form a surface that resists stress concentration.

[0015] Optionally, depositing an insulating dielectric layer on the surface of the repaired tank body and forming a continuous encapsulation protective layer on the tank wall and bottom by a vacuum coating process specifically includes the following steps: A mixed gas of argon and oxygen with a volume ratio of 4:1 is introduced into the vacuum chamber, and radio frequency power is applied to generate low-temperature plasma to etch and activate the surface of the micro-nanostructure of the groove wall. Gradient magnetron sputtering is implemented to deposit a first-thickness Cr transition layer and a second-thickness aluminum oxide insulating layer in sequence. By adjusting the substrate rotation speed in real time, full coverage deposition of the three-dimensional structure of the slot is achieved. After the post-processing of the encapsulation layer is completed, the temperature is raised to 350-400°C at a rate of 10°C / s under nitrogen protection for rapid thermal annealing, and an axial magnetic field is simultaneously applied to induce preferential grain orientation so that the density of the film layer reaches the qualified density value.

[0016] Compared with the existing technology, the present invention has the following beneficial effects: first, the surface of the rigid layer of the soft-hard combination circuit board is mechanically ground and pre-treated to reduce the roughness, and a laser sensitive layer containing a wavelength-selective absorption material is sprayed; then, CNC depth-controlled milling is used to form a slotted rough structure; a three-dimensional correction model containing the distribution of optical materials is established by laser scanning reflection signals; based on the model data, the second power laser fine cutting and the third power laser depth calibration are implemented in stages to form a stepped transition groove body; then, ultraviolet laser scanning is combined with low-temperature gas purging to simultaneously remove the residue at the bottom of the groove and inhibit the expansion of the heat-affected zone, thereby completing high-precision and low-damage slotting processing; this process realizes high-precision depth-controlled slotting of the soft-hard combination circuit board by integrating laser sensitive layer regulation, three-dimensional modeling compensation and stepped energy output, while having ultra-low thermal damage, anti-fatigue structure and long-term environmental stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0019] Figure 1 This is one of the flow diagrams of the grooving process for a rigid-flexible circuit board based on the laser depth control technology of this embodiment; Figure 2 This is the second flow chart of the rigid-flexible circuit board slotting process based on the laser depth control technology of this embodiment; Figure 3Schematic diagram of circuit board processing for the rigid-flexible circuit board slotting process based on laser depth control technology in this embodiment. DETAILED DESCRIPTION

[0020] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0023] Combine Figures 1 to 3 As shown, the embodiment of the present invention provides a grooving process for a rigid-flexible circuit board based on laser depth control technology, comprising the following steps: S1, pre-treating the surface of the rigid layer of the rigid-flex circuit board 100. Specifically, the pre-treatment includes first reducing the surface roughness by mechanical grinding and spraying a laser-sensitive layer 101 on the surface. The laser-sensitive layer 101 contains an optical material for wavelength-selective absorption. Mechanical grinding reduces the surface roughness of the rigid layer, eliminating the scattering interference of microscopic bumps and irregularities on the laser beam, and provides a smooth substrate for the subsequent uniform coating of the laser-sensitive layer 101. The sprayed wavelength-selective absorption layer enhances the energy coupling efficiency of lasers in specific wavelength bands, reduces ineffective heat diffusion, and ensures a clear energy threshold for the subsequent ablation process.

[0024] S2 uses CNC-controlled depth milling to create a slotted rough structure on the pretreated rigid layer surface. This pre-grooved rough structure is mechanically removed through CNC-controlled depth milling, avoiding the prolonged heat exposure associated with direct laser processing. The milling depth is controlled within a preset range (50-100μm) from the target groove bottom, minimizing subsequent laser processing while leaving sufficient buffer space to prevent overcutting and damage to the flexible layer.

[0025] S3, laser scanning modeling of the slotted blank structure, and establishing a three-dimensional model including optical material density and thickness distribution through the collected reflection signals; Positioning laser scanning is used to acquire reflected signal intensity and phase information. Combined with material optical property differences, this allows reverse engineering to deduce the material density gradient within the rigid layer and the thickness distribution of the adhesive layer. The 3D model quantitatively characterizes the energy absorption characteristics of the processed area, providing physical field data support for adaptive adjustment of layered ablation parameters and avoiding ablation depth deviations caused by material inhomogeneities.

[0026] S4, performing laser finishing based on the three-dimensional corrected model, sequentially using a second power laser for finishing cutting and a third power laser for depth calibration, to form a stepped transition trough structure 102; Based on a 3D model, different power domains are defined, and a stepped energy progression strategy is used to achieve layer-by-layer material removal: high-power rough cutting for rapid depth control, medium-power fine-tuning to adjust the groove wall topography, and low-power annular spot calibration to ensure the desired depth. This layered, multi-stage processing mode dynamically distributes energy to reduce single-pass heat input, alleviating thermal stress accumulation at the rigid / flexible interface.

[0027] S5, cleaning the processed groove interface, switching to ultraviolet laser scanning groove bottom area and simultaneously introducing low-temperature gas to remove residual adhesive and inhibit the expansion of the heat-affected zone; The high photon energy of the UV laser effectively breaks the adhesive's molecular chains, while the low-temperature nitrogen flow suppresses the expansion of the heat-affected zone and accelerates the vaporization and discharge of decomposition products. The synergistic effect of laser parameters and the cooling medium thoroughly removes interface residues while maintaining the structural integrity of the polyimide insulation layer.

[0028] S6, performing a morphology repair process on the cleaned groove surface, using a short pulse laser to generate a periodic groove structure 103 on the groove wall to form a surface that resists stress concentration; The short pulse width of the laser suppresses the conduction of thermal effects. By precisely controlling the interaction between the laser and the material, a periodic groove structure is induced on the groove wall surface. 103 This structure can change the stress distribution pattern, dispersing concentrated stress across multiple microstructural units, thereby improving the fatigue resistance of the flexible layer under dynamic bending conditions.

[0029] S7, depositing an insulating dielectric layer 104 on the surface of the repaired slot body, and forming a continuous encapsulation protection layer on the slot wall and bottom through a vacuum coating process.

[0030] The vacuum coating process deposits a dense insulating layer in a low-contamination environment. Its stepped deposition parameters ensure a continuous, encapsulated layer covering the three-dimensional surface of the slot. This protective layer not only provides electrical insulation but also blocks the penetration of ambient moisture and contaminants, ensuring long-term reliability in the rigid-flex transition region under complex operating conditions.

[0031] The working principle of the present invention is as follows: first, the surface of the rigid layer of the soft-rigid combination circuit board 100 is pretreated, the roughness is reduced by mechanical grinding and a laser sensitive layer 101 with wavelength selective absorption characteristics is sprayed; then a positioning laser is used to scan the slotted area, and a three-dimensional model containing material density and thickness distribution is constructed based on the reflected signal; according to the model data, a stepped slot structure 102 is formed by layered controlled depth ablation of high, medium and low power lasers in sequence; an ultraviolet laser is used to scan the bottom of the slot and low-temperature gas is introduced to remove residual adhesive and inhibit the expansion of the heat-affected zone; a short-pulse laser is used to generate a periodic slot structure 103 on the slot wall to optimize the stress distribution; finally, an insulating dielectric layer 104 is deposited on the slot surface, and a continuous packaging protective layer is formed by vacuum coating to achieve full Process processing; This process achieves precise control of the ablation depth of the rigid layer and avoids damage to the flexible layer through the synergistic effect of the wavelength-selective laser sensitive layer 101 and three-dimensional modeling; layered depth-controlled ablation combined with a stepped structure design significantly reduces the risk of thermal stress accumulation and material delamination; UV laser cleaning and low-temperature gas synergistically reduce the width of the heat-affected zone and eliminate interface residues; the groove wall and groove structure 103 improves the bending fatigue life of the flexible layer; the vacuum packaging layer effectively isolates the environmental erosion, so that the groove structure 102 maintains stable electrical performance in a high temperature and high humidity environment, and through multi-modal laser collaborative processing and dynamic closed-loop control, high-precision depth-controlled grooving of the soft-hard combined circuit board 100 is achieved, while also having ultra-low thermal damage, fatigue-resistant structure and long-term environmental stability.

[0032] In this embodiment, the laser sensitive layer 101 is specifically composed of: 30%~45% wavelength selective absorber, 50%~65% thermal stability binder and 5%~8% dispersing agent; The absorber concentration range of 30%-45% ensures efficient absorption of 1064nm laser (≥90%) while avoiding coating embrittlement caused by excessive addition; the binder ratio of 50%-65% ensures the adhesion of the coating to the rigid substrate and dimensional stability at high temperatures; the dispersing agent ratio of 5%-8% can effectively inhibit the agglomeration of nanoparticles and ensure coating uniformity.

[0033] The thickness of the laser sensitive layer 101 is 8-15 μm, the absorption rate of the laser with a wavelength of 1064 nm is ≥90%, and the reflectivity of the laser with a wavelength of 355 nm is ≥85%.

[0034] The thickness range of 8-15μm matches the penetration depth requirements of laser ablation. Too thin may lead to insufficient energy absorption, while too thick may increase process costs. The 1064nm absorption rate of ≥90% ensures efficient utilization of processing laser energy, and the 355nm reflectivity of ≥85% provides optical isolation protection for subsequent UV cleaning processes.

[0035] In this embodiment, it is further explained that the wavelength selective absorber is composed of carbon nanotubes and iron oxide composite nanoparticles, wherein the mass ratio of carbon nanotubes to iron oxide is 1:2~1:4; the thermally stable binder is selected as silicone-modified epoxy resin; and the dispersing aid is selected as polyether-modified silicone.

[0036] It should be noted that carbon nanotubes provide broadband absorption characteristics and electrical and thermal conduction pathways, while iron oxide nanoparticles enhance the localized surface plasmon resonance effect of near-infrared light. The 1:2-1:4 mass ratio forms the best synergistic absorption ratio between the two, which not only avoids the enhanced laser scattering caused by excessive carbon nanotubes, but also prevents the decrease in thermal stability caused by an excessive proportion of iron oxide.

[0037] In this embodiment, it is specifically described that step S2 specifically includes: S21, planning the laser scanning path, generating a scanning trajectory according to the preset boundary coordinates of the slotted blank structure, setting the line spacing of the scanning trajectory to 1 / 3 of the laser spot diameter, and presetting a dynamic focus compensation range of 0.05-0.2 mm along the Z-axis direction; By setting the scan line spacing to 1 / 3 of the laser spot diameter, we ensure moderate overlap between adjacent scan tracks, avoiding local data loss due to excessive gaps and suppressing the heat accumulation effect caused by excessive overlap. A preset dynamic focus compensation range (0.05-0.2mm) allows the laser focus to adapt to surface fluctuations, ensuring real-time matching of the focal plane with the material surface during scanning, establishing stable optical conditions for subsequent signal acquisition.

[0038] S22, performing multispectral reflection signal acquisition, using a 532nm green laser with a pulse power of 8-12W to illuminate the surface of the rigid layer along a scanning trajectory, synchronously receiving the 532nm fundamental frequency light intensity signal and the 1064nm second harmonic signal in the reflected light, and establishing a material absorption characteristic distribution map; A 532nm green laser with a power range of 8-12W is used to stimulate the surface response. Its wavelength allows it to penetrate the laser-sensitive layer 101 without damaging the substrate. Both the fundamental frequency intensity signal and the second harmonic signal are collected simultaneously. The former reflects the macroscopic absorption characteristics of the surface, while the latter enhances sensitivity to the chemical bonding state of the material through nonlinear optical effects. Dual-spectral data fusion enables a more comprehensive characterization of the material's photothermal response characteristics, providing multidimensional physical field information for modeling.

[0039] S23, performing interferometric measurement modeling, directing part of the reflected light into the interferometer through a beam splitter prism, calculating the surface height change based on the displacement of the interference fringes, and generating initial three-dimensional profile data; A beam splitter prism directs the reflected light into an interferometer, where the displacement of the interference fringes is used to calculate surface height variations. Compared to traditional confocal measurement, interferometry offers higher longitudinal resolution, enabling precise capture of microscopic relief features on rigid surfaces.

[0040] S24, fusing the multimodal data to establish a physical field model, inputting the material absorption characteristic distribution map and the three-dimensional contour data into a finite element algorithm, combining the dielectric constant gradient parameter of the laser sensitive layer 101, and inversely calculating the material density distribution inside the rigid layer and the adhesive interface thickness to establish a three-dimensional model; The absorption characteristic distribution and 3D profile data are fed into a finite element method, combined with the dielectric constant gradient parameter of the laser-sensitive layer 101, to achieve an inverse calculation of the material density and adhesive thickness. This multimodal fusion method overcomes the limitations of a single data source, revealing the internal structural characteristics of the material through physical field coupling, significantly improving the model's adaptability to actual processing scenarios.

[0041] S25, dynamically calibrating the energy absorption threshold of the slotted area in the three-dimensional model according to the density-thickness coupling relationship, generating a digital processing map including ablation priority marks to optimize the three-dimensional model.

[0042] Dynamically calibrating the energy absorption threshold based on the density-thickness coupling relationship transforms the theoretical model into an executable processing strategy. The introduction of ablation priority markings enables differentiated energy allocation, prioritizing high-density / thick adhesive areas, avoiding over- or under-burning issues caused by uniform energy input, and improving processing efficiency and consistency.

[0043] In this embodiment, it is specifically explained that step S3 specifically includes the following steps: S31, analyzing the ablation priority mark in the three-dimensional model, dividing the slotting area into a core ablation area and an edge transition area, wherein the core ablation area is set as a first power laser action area, and the edge transition area is set as a second power laser action area; By analyzing the ablation priority markers on the 3D model, the slotting area is divided into a core zone and an edge transition zone. A high-power laser is used to rapidly remove the bulk material in the core zone, while a low-power laser is used to finely trim the edge zone. This strategy precisely distributes energy based on material density distribution, avoiding undercutting of high-density areas or overburning of low-density areas due to uniform power input, while also leaving a machining margin for subsequent taper angle control.

[0044] S32, performing a first power laser rough cutting, using an infrared laser with a peak power of 30-50W and a pulse width of 200-400ns to scan along the core area at a scanning speed of 400-600mm / s to complete the depth control of the first depth of the groove area, and synchronously triggering the plasma spectrum monitoring module to determine the residual amount of glass fiber in real time; Using an infrared laser with a peak power of 30-50W and a pulse width of 200-400ns, the system efficiently removes the bulk material from the rigid layer at a scanning speed of 400-600mm / s. Simultaneously triggering plasma spectral monitoring, the system analyzes the intensity changes of the glass fiber's characteristic spectral lines (such as the Si-O bond vibration peak) to determine the residual amount in real time. This combined design ensures processing efficiency while providing a quantitative basis for subsequent process adjustments.

[0045] S33, implement adaptive energy gradient regulation, dynamically adjust the second power laser parameters according to the residual data, use 18-25W power and 100-150ns pulse width in the edge transition area, and perform oblique scanning at a speed of 800-1000mm / s to form a groove structure 102 with a groove wall cone angle of 5-15°.

[0046] S34 uses a third-power laser combined with an annular spot to perform depth calibration of spiral refinement along the groove bottom contour at a speed of 1200-1500mm / s, and uses a confocal sensor to feedback and compensate for depth deviation in real time; specifically, the annular spot is set to an outer ring diameter of 80-120μm and an inner ring diameter of 30-50μm.

[0047] Spiral finishing is performed using an annular spot with an outer diameter of 80-120μm and an inner diameter of 30-50μm. Its hollow beam characteristics evenly distribute energy at the groove bottom. High scanning speeds of 1200-1500mm / s, matched to the real-time feedback frequency of the confocal sensor, achieve precise depth control. This design effectively eliminates the raised groove bottom defect caused by excessive center energy in traditional Gaussian spot processing.

[0048] S35 , performing cross-layer thermal stress equalization processing, inserting a 50-100 μs delay period after each power cutting is completed, and applying a 10-20 kHz high-frequency pulse to perform micro-impact on the cutting surface to eliminate the interlayer stress concentration of the slot structure 102 .

[0049] A 50-100μs delay period is inserted after each layer is processed to allow the material thermal relaxation process to be completed. The mechanical micro-shock waves generated by the 10-20kHz high-frequency pulse promote the reorganization of lattice dislocations and release residual stress.

[0050] In this embodiment, it is specifically explained that step S4 specifically includes the following steps: S41, setting the cryogenic gas coordination parameters, regulating the nitrogen jet temperature (-50°C to -30°C) and flow rate (5-15 L / min) according to the depth gradient distribution of the groove body, forming an axial temperature gradient field at the bottom of the groove, causing differential thermal strain in the adhesive and polyimide layer; By regulating the nitrogen jet temperature (-50°C to -30°C) and flow rate (5-15 L / min), an axial temperature gradient field is created at the bottom of the groove. This leverages the difference in thermal expansion coefficients between the adhesive (CTE ≈ 150 ppm / °C) and the polyimide (CTE ≈ 40 ppm / °C) to induce directional thermal strain at the interface. This design weakens the bond between the adhesive and the substrate through a thermal-mechanical coupling effect, providing pre-stripping conditions for subsequent laser cleaning. The low temperature environment also suppresses heat diffusion caused by the laser.

[0051] S42, performing multi-mode laser cleaning, using a 355nm UV laser with a frequency of 20-30kHz and a power of 5-8W for spiral scanning. In the initial stage, a Gaussian spot is used to remove loose adhesive on the surface, and in the later stage, a flat-top spot is used to remove interface-bound residues. Initially, a Gaussian spot (energy density gradient distribution) is used to efficiently remove loose adhesive from the surface. Later, a flat-top spot (uniform energy distribution) is used to remove chemically bonded residues from the interface. The high photon energy (3.5 eV) of the 355 nm UV laser selectively breaks the adhesive's molecular chains (C-C bond energy ≈ 3.6 eV). The 20-30 kHz frequency matches the material's thermal relaxation period (10-50 μs), achieving a balance between removal efficiency and thermal damage control.

[0052] S43, implementing dynamic energy coupling regulation, based on the real-time infrared thermal imaging data feedback of the temperature field change at the bottom of the groove, dynamically adjusting the laser duty cycle and gas flow rate to ensure that the local temperature rise is always lower than the glass transition temperature of the polyimide; Based on real-time feedback from infrared thermal imaging data on the temperature distribution at the bottom of the groove, the laser duty cycle (10-40%) and gas flow rate (5-15 L / min) are dynamically adjusted, forming a negative feedback control loop. This mechanism limits local temperature rise (to less than 280°C, the glass transition point of polyimide), preventing pyrolysis and carbonization of the flexible layer while ensuring the effective removal of thermal decomposition products of the adhesive.

[0053] S44, by online detection of the characteristic peak of the groove bottom, the cleaning is terminated when the residual adhesive signal intensity is less than the preset threshold, and the heat-affected zone width data is simultaneously recorded for process iterative optimization.

[0054] The signal intensity of the characteristic peak of the adhesive is monitored online by Raman spectroscopy. When the residual amount is less than the threshold of 3%, the cleaning is terminated to avoid excessive treatment and damage to the polyimide substrate. In this embodiment, it is specifically explained that step S5 specifically includes the following steps: S51, pre-treating the contaminants on the tank wall surface, using laser (wavelength 515nm, pulse width 400-600fs) at 0.5-1.5J / cm 2 The energy density is scanned over the entire area to remove the nano-scale oxide layer and activate the surface chemical bond activity; A 515 nm laser was used at 0.5-1.5 J / cm 2 The energy density is scanned across the entire surface, and its ultrashort pulse width suppresses thermal diffusion, removing the nanoscale oxide layer through photo-stripping. Simultaneously, laser-induced surface electron excitation exposes chemically active sites. This pretreatment provides a clean and highly reactive interface for subsequent processing of the slot structure 103, improving the energy coupling efficiency between the laser and the material.

[0055] S52, constructs a dual-beam interference processing field, splitting a short-pulse laser into two coherent beams to form interference fringes with adjustable spatial period on the groove wall surface. The phase difference is controlled by a piezoelectric ceramic translation stage to induce plasmon-enhanced ablation on the surface. A short laser pulse is split into two coherent beams. The optical path difference is adjusted using a piezoelectric ceramic stage, forming spatially periodic interference fringes on the groove wall surface. Plasmon enhancement localizes the laser energy to the antinodes of the interference field, enabling selective ablation with subwavelength precision. This technology breaks through the diffraction limit and produces high-precision periodic structures while avoiding thermal damage.

[0056] S53, performing gradient energy etching, adjusting the laser flux in three sections along the depth direction of the groove body, generating a parallel groove structure in the groove mouth area, a scale-like stacked structure in the middle of the groove, and a radial corrugated structure at the groove bottom, thereby generating a periodic groove structure 103 on the groove wall; The laser flux is adjusted in three sections along the depth of the tank (0.8-1.2J / cm 2 Parallel grooves in the notch area enhance bending resistance by directional stress dispersion; a scale-like laminated structure in the middle of the notch utilizes biomimetic geometry to enhance interlayer bonding strength; and radial ripples (wavelength 150-250nm) at the bottom of the notch inhibit crack propagation through multi-directional stress transfer. The gradient design aligns the notch structure 103 with the actual stress distribution, maximizing stress concentration resistance.

[0057] S54, performing dynamic stress compensation, applying 40-60kHz ultrasonic vibration during laser processing, dynamically adjusting the laser repetition frequency and scanning speed, so that the residual stress of the periodic groove structure 103 is reduced to a qualified threshold, forming a stress concentration resistant surface.

[0058] In this embodiment, it is specifically explained that step S6 specifically includes the following steps: S61, introducing an argon / oxygen mixed gas with a volume ratio of 4:1 into the vacuum chamber, applying radio frequency power to generate low-temperature plasma, and etching and activating the surface of the groove wall and groove body structure 103 to activate the surface; An argon / oxygen mixture (4:1 by volume) is introduced, and 200-400W of radio frequency power is applied. The argon gas physically cleans the surface through ion bombardment, while the oxygen participates in chemical reactions to remove organic contaminants and introduce reactive groups such as hydroxyl groups. Low-temperature plasma (electron temperature 3-5eV) etches the surface roughness of the slot structure 103 (Ra = 0.1 → 0.4μm), while avoiding thermal damage. The activated surface energy (60-72mN / m) significantly enhances film adhesion.

[0059] S62, performing gradient magnetron sputtering coating to deposit a Cr transition layer of a first thickness and an aluminum oxide insulating layer of a second thickness in sequence, and achieving full coverage deposition of the three-dimensional structure of the slot by adjusting the substrate rotation speed in real time; A first-thick Cr transition layer is deposited (800-1200W power, -150V bias). Its high ductility alleviates thermal expansion mismatch stress between the substrate and the insulating layer. A second-thick aluminum oxide insulating layer is then applied (1500-2000W power, -300V bias). Its amorphous structure provides stable dielectric properties. By adjusting the substrate rotation speed in real time, centrifugal force is used to improve film thickness uniformity on the sidewalls and bottom of the tank.

[0060] S63, complete the post-processing of the encapsulation layer, and perform rapid thermal annealing at a rate of 10°C / s to 350-400°C under nitrogen protection, and simultaneously apply an axial magnetic field to induce preferential grain orientation so that the density of the film layer reaches the qualified density value.

[0061] Under nitrogen protection, the temperature is raised to 350-400°C at a rate of 10°C / s. Rapid thermal annealing promotes the transformation of amorphous aluminum oxide into the gamma phase, eliminating porosity within the film. Simultaneously, a 0.5-1.2T axial magnetic field is applied, inducing the preferred orientation of grains along the surface using the Lorentz force, forming a dense columnar structure. This combined treatment increases the density of the film, significantly enhancing its moisture resistance and mechanical strength.

[0062] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A slotting process for a rigid-flexible circuit board based on laser depth control technology, characterized in that: The following steps are involved: Pre-treating the surface of the rigid layer of the rigid-flex circuit board by mechanically grinding to reduce the surface roughness and spraying a laser-sensitive layer on the surface. The laser-sensitive layer contains an optical material for wavelength-selective absorption. CNC controlled deep milling is used to form a slotted rough structure on the surface of the pre-treated rigid layer; Performing laser scanning modeling on the slotted blank structure, and establishing a three-dimensional model including optical material density and thickness distribution through the collected reflection signals; Laser finishing is performed based on the three-dimensional corrected model, and a second power laser is used for fine cutting and a third power laser is used for depth calibration in sequence to form a stepped transition groove structure; The processed groove interface is cleaned, the ultraviolet laser is switched to scan the groove bottom area and low-temperature gas is introduced simultaneously to remove residual adhesive and inhibit the expansion of the heat-affected zone.

2. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1 is characterized in that: The process of cleaning the processed groove interface, switching the ultraviolet laser to scan the groove bottom area and simultaneously introducing low-temperature gas to remove residual adhesive and inhibit the expansion of the heat-affected zone also includes: The cleaned groove surface is repaired by using a short-pulse laser to generate a periodic micro-nano structure on the groove wall to form a surface that resists stress concentration. An insulating dielectric layer is deposited on the surface of the repaired slot body, and a continuous encapsulation protective layer is formed on the slot wall and bottom through a vacuum coating process.

3. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1, characterized in that: The specific composition of the laser sensitive layer is: 30%~45% wavelength selective absorber, 50%~65% thermal stability binder and 5%~8% dispersing agent; The thickness of the laser sensitive layer is 8-15 μm, the absorption rate of the laser with a wavelength of 1064 nm is ≥90%, and the reflectivity of the laser with a wavelength of 355 nm is ≥85%.

4. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 3 is characterized in that: The wavelength selective absorber is composed of carbon nanotubes and iron oxide composite nanoparticles, wherein the mass ratio of carbon nanotubes to iron oxide is 1:2 to 1:4; the thermal stability binder is selected as a siloxane-modified epoxy resin; The dispersing aid is polyether-modified siloxane.

5. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1, characterized in that: Laser scanning modeling is performed on the slotted blank structure, and a three-dimensional model including the density and thickness distribution of the optical material is established through the collected reflection signals, specifically including: Planning a laser scanning path, generating a scanning trajectory according to the preset boundary coordinates of the slotted blank structure, setting the line spacing of the scanning trajectory to 1 / 3 of the laser spot diameter, and presetting a dynamic focus compensation interval of 0.05-0.2 mm along the Z-axis direction; Perform multispectral reflection signal acquisition, using a 532nm green laser with a pulse power of 8-12W to illuminate the surface of the rigid layer along the scanning trajectory, synchronously receiving the 532nm fundamental frequency light intensity signal and the 1064nm second harmonic signal in the reflected light, and establishing a material absorption characteristic distribution map; Implement interferometric measurement modeling, guide part of the reflected light into the interferometer through a beam splitter prism, calculate the surface height change based on the displacement of the interference fringes, and generate initial 3D profile data; The multimodal data is integrated to establish a physical field model. The material absorption characteristic distribution map and 3D contour data are input into the finite element algorithm. Combined with the dielectric constant gradient parameters of the laser-sensitive layer, the material density distribution inside the rigid layer and the adhesive interface thickness are inversely calculated to establish a 3D model. The energy absorption threshold of the slotted area in the three-dimensional model is dynamically calibrated according to the density-thickness coupling relationship, and a digital processing map including ablation priority marks is generated to optimize the three-dimensional model.

6. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 5, characterized in that: The laser finishing based on the three-dimensional corrected model, sequentially using the second power laser for fine cutting and the third power laser for depth calibration to form a stepped transition trough structure, specifically includes the following steps: Analyze the ablation priority mark in the three-dimensional model and divide the slotting area into a core ablation area and an edge transition area, where the core ablation area is set as the first power laser action area and the edge transition area is set as the second power laser action area; Perform the first power laser rough cutting, using an infrared laser with a peak power of 30-50W to scan along the core area at a scanning speed of 400-600mm / s to complete the depth control of the first depth of the slotted area, and synchronously trigger the plasma spectrum monitoring module to determine the residual amount of glass fiber in real time; Adaptive energy gradient regulation is implemented, and the second power laser parameters are dynamically adjusted according to the residual data. In the edge transition zone, 18-25W power is used and oblique scanning is performed at a speed of 800-1000mm / s to form a groove structure with a groove wall taper angle of 5-15°. Using a third-power laser with an annular spot, the depth calibration of spiral finishing is performed along the groove bottom contour at a speed of 1200-1500mm / s. The depth deviation is fed back and compensated in real time through the confocal sensor. A cross-layer thermal stress equalization process is performed, a preset delay period is inserted after each power cutting is completed, and a high-frequency pulse is applied to perform micro-impact on the cutting surface to eliminate the interlayer stress concentration of the trough structure.

7. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 6, characterized in that: The annular light spot is set to have an outer ring diameter of 80-120 μm and an inner ring diameter of 30-50 μm.

8. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1, characterized in that: The process of cleaning the processed groove interface, switching the ultraviolet laser to scan the groove bottom area and simultaneously introducing low-temperature gas to remove residual adhesive and inhibit the expansion of the heat-affected zone specifically includes the following steps: The low-temperature gas synergy parameters are set, and the nitrogen jet temperature and flow rate are controlled according to the depth gradient distribution of the groove body. An axial temperature gradient field is formed at the bottom of the groove, which causes differential thermal strain in the adhesive and polyimide layer. Perform multi-mode laser cleaning, using a 355nm UV laser with a frequency of 20-30kHz and a power of 5-8W for spiral scanning. In the initial stage, a Gaussian spot is used to remove loose adhesive on the surface, and in the later stage, a flat-top spot is used to remove interface-bound residues. Implement dynamic energy coupling regulation, based on the real-time infrared thermal imaging data feedback of the temperature field changes at the bottom of the tank, and dynamically adjust the laser duty cycle and gas flow rate to ensure that the local temperature rise is always lower than the glass transition temperature of the polyimide; By online detection of the characteristic peaks at the bottom of the groove, cleaning is terminated when the residual adhesive signal intensity is less than the preset threshold, and the heat-affected zone width data is simultaneously recorded for process iterative optimization.

9. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1, characterized in that: The morphology repair process of the cleaned groove surface is performed, and a short pulse laser is used to generate a periodic micro-nano structure on the groove wall to form a stress concentration resistant surface, which specifically includes the following steps: Pre-treat the contaminants on the tank wall surface by using laser to perform full-area scanning to remove the nano-scale oxide layer and activate the surface chemical bond activity; A dual-beam interference processing field is constructed to split the short-pulse laser into two coherent beams, forming interference fringes with adjustable spatial period on the groove wall surface. The phase difference is controlled by a piezoelectric ceramic translation stage to induce plasmon-enhanced ablation on the surface. Gradient energy etching is performed, and the laser flux is adjusted in three sections along the depth direction of the groove body. A parallel groove structure is generated in the groove area, a scale-like stacked structure is generated in the middle of the groove, and a radial corrugated structure is generated at the bottom of the groove, thereby generating a periodic micro-nano structure on the groove wall. Perform dynamic stress compensation, apply 40-60kHz ultrasonic vibration during laser processing, dynamically adjust the laser repetition frequency and scanning speed, reduce the residual stress of the periodic micro-nano structure to the qualified threshold, and form a surface that resists stress concentration.

10. The grooving process for a rigid-flexible circuit board based on laser depth control technology according to claim 1, characterized in that: Depositing an insulating dielectric layer on the surface of the repaired tank body and forming a continuous encapsulation protective layer on the tank wall and bottom by a vacuum coating process specifically includes the following steps: A mixed gas of argon and oxygen with a volume ratio of 4:1 is introduced into the vacuum chamber, and radio frequency power is applied to generate low-temperature plasma to etch and activate the surface of the micro-nanostructure of the groove wall. Gradient magnetron sputtering is implemented to deposit a first-thickness Cr transition layer and a second-thickness aluminum oxide insulating layer in sequence. By adjusting the substrate rotation speed in real time, full coverage deposition of the three-dimensional structure of the slot is achieved. After the post-processing of the encapsulation layer is completed, the temperature is raised to 350-400°C at a rate of 10°C / s under nitrogen protection for rapid thermal annealing, and an axial magnetic field is simultaneously applied to induce preferential grain orientation so that the density of the film layer reaches the qualified density value.

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