Laser processing system and laser processing method for metal coating on hole wall

Abstract

A laser processing system and a laser processing method for a metal coating on a hole wall. A laser generation module of the system is configured to generate an initial laser beam. A beam diameter and divergence angle dynamic control module is configured to adjust the diameter and the divergence angle of the initial laser beam to form an adjusted beam whose diameter is proportionally matched with the thickness of the metal coating. An annular beam dynamic focusing module is configured to shape the adjusted beam into an annular beam matching the cross-sectional shape of the metal coating and to refract a branch beam, and by monitoring the laser energy and the beam diameter of the branch beam, acquire dynamic parameters of the laser energy and the beam diameter of the annular beam. A focus three-dimensional offset module is configured to dynamically adjust a focus of the annular beam on the basis of the laser energy and the beam diameter of the annular beam and the depth of a non-drillable layer.

Description

Laser processing system and hole wall metal plating layer laser processing method

[0001] This application claims priority to the Chinese patent application No. 202410530235.5, filed on April 29, 2024, with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of printed circuit board production, for example to a laser processing system and a hole wall metal plating layer laser processing method. BACKGROUND

[0003] Printed circuit boards are structures of multiple layers of circuits. To achieve signal interconnection across layers, holes are drilled at reserved nodes of two board layers to be connected to communicate the two layers, and a metal plating layer is formed on the hole wall by electroplating process to electrically connect the two board layers to be connected.

[0004] When the two board layers that need to be electrically connected are both located in the inner layers of the printed circuit board, the metal plating layer covers the entire hole wall, and only the metal plating layer segment between the two board layers actually plays an electrical connection role, i.e., there is a large amount of redundant metal plating layer. For printed circuit boards used for high-speed transmission, the redundant metal plating layer not only destroys the impedance continuity, but also seriously affects the transmission of high-frequency high-speed signals.

[0005] Based on the above reasons, the related art means for processing the redundant metal plating layer is to drill and remove the redundant metal plating layer in a manner similar to hole expansion after the metal plating layer is formed in the hole wall. However, due to the drill bit angle, the drill bit rotates to form a reverse cone-shaped downhole cutting zone, and in order to ensure the electrical connection quality of the effective metal plating layer segment, the board layer to be connected located at a relatively shallow position is defined as a non-drillable layer, thereby limiting the cutting depth. When the tip of the downhole cutting zone reaches the limit position of the non-drillable layer, the metal plating layer located at the edge of the downhole cutting zone still has a segment of residual metal plating layer beyond the non-drillable layer, which is called residual stub in the industry. The residual stub also affects the impedance continuity and the transmission performance of high-frequency high-speed signals.

[0006] In summary, there is an urgent need for a method to minimize or even completely remove the residual stub to improve the performance of printed circuit boards used for high-speed transmission. SUMMARY

[0007] The present application provides a laser processing system that can minimize or even completely remove the residual stub in the hole, and has high precision when removing the residual stub site.

[0008] The present application provides the following technical solutions:

[0009] The application provides a laser processing system, which comprises a laser generating module, a beam diameter and divergence angle dynamic control module, a ring-shaped beam dynamic focusing module and a focal point three-dimensional offset module arranged on the same laser path.

[0010] The laser generating module is arranged to generate an initial light beam.

[0011] The beam diameter and divergence angle dynamic control module is arranged to adjust the diameter and divergence angle of the initial light beam to form an adjusted light beam with a diameter matching the thickness of the metal coating.

[0012] The ring-shaped beam dynamic focusing module is arranged to shape the adjusted light beam into a ring-shaped light beam matching the cross-sectional shape of the metal coating and refract a branch light beam, and the laser energy and the beam diameter of the ring-shaped light beam are obtained by monitoring the laser energy and the beam diameter of the branch light beam.

[0013] The focal point three-dimensional offset module is arranged to dynamically adjust the focal point of the ring-shaped light beam according to the laser energy and the beam diameter of the ring-shaped light beam and the depth of the non-drillable layer.

[0014] The application also provides the following technical solutions: a hole wall metal coating laser processing method applied to the laser processing system, which comprises the following steps.

[0015] The position coordinates, diameter and depth of the drill hole are measured, the depth coordinates of the non-drillable layer, the thickness and the cross-sectional shape of the metal coating are detected;

[0016] The laser generating module is started to generate an initial light beam, and the laser path is adjusted according to the position coordinates of the drill hole so that the light spot of the initial light beam on the printed circuit board covers the drill hole.

[0017] The diameter and divergence angle of the initial light beam are adjusted by the beam diameter and divergence angle dynamic control module to output an adjusted light beam with a diameter matching the thickness of the metal coating.

[0018] The adjusted light beam is secondarily shaped according to the cross-sectional shape of the metal coating and the thickness of the metal coating by the ring-shaped beam dynamic focusing module to output a ring-shaped light beam matching the cross-sectional shape of the metal coating, the thickness of the metal coating and the diameter of the drill hole.

[0019] A part of the ring-shaped light beam is extracted to form a branch light beam by the ring-shaped beam dynamic focusing module, and the branch light beam is monitored in at least one of the following ways: laser energy monitoring and beam diameter monitoring.

[0020] The laser energy monitoring of the branch light beam comprises: converting the monitoring branch light beam laser energy into monitoring annular light beam laser energy by adjusting the branch light beam and the annular light beam in a proportional manner; in response to determining that the laser energy of the annular light beam is lower than 90% of the calibration energy, adjusting the focal point position of the annular light beam so that the percentage of the laser energy of the annular light beam to the calibration energy is between 90% and 100%;

[0021] The beam diameter monitoring of the branch light beam comprises: monitoring the diameter of the annular light beam synchronously by monitoring the diameter change of the branch light beam by adjusting the branch light beam and the annular light beam in a proportional manner; in response to determining that the diameter deviation of the annular light beam from the hole diameter of the drilled hole exceeds ±10%, adjusting the focal point position of the annular light beam so that the deviation is less than or equal to 10%;

[0022] According to the depth coordinates of the non-drillable layer and the depth of the drilled hole, the movement distance of the focal point of the annular light beam is limited to be less than the depth of the drilled hole until the residual pile removal is completed. BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a structural schematic diagram of a laser processing system according to an embodiment of the present application.

[0024] FIG. 2 is a cross-sectional view of an annular light beam according to an embodiment of the present application.

[0025] FIG. 3 is a front view of an annular light beam according to an embodiment of the present application.

[0026] FIG. 4 is a schematic diagram of an annular light beam focusing to process a metal plating layer on a hole wall according to an embodiment of the present application.

[0027] FIG. 5 is a schematic diagram of an annular light beam defocusing to process a metal plating layer on a hole wall according to an embodiment of the present application. DETAILED DESCRIPTION

[0028] As shown in FIG. 1, the embodiment discloses a laser processing system, which comprises a laser generation module, a beam diameter and divergence angle dynamic control module, an annular light beam dynamic focusing module, and a focal point three-dimensional offset module. A laser beam generated by the laser generation module is refracted and / or reflected by multiple mirror structures to form a spot on the surface of a printed circuit board, and the route of the laser beam is a laser path. Since the multiple modules are respectively arranged to adjust the laser beam, the arrangement positions of the multiple modules are adjusted to the laser beam on the laser path. In order to clearly express the effect of the multiple modules on the laser beam, the new state of the laser beam output after being processed by the multiple modules is named in segments. The processing flow of the laser processing system is as follows:

[0029] The laser beam generated by the laser generation module is named as an initial beam. The initial beam enters the beam diameter and divergence angle dynamic control module for preliminary shaping processing. By adjusting the divergence angle, the diameter of the initial beam is changed, so that the diameter of the adjusted initial beam is proportional to the thickness of the metal coating, and the initial beam after the completion of the outer contour shaping is renamed as an adjusted beam. The adjusted beam enters the annular beam dynamic focusing module and is adjusted again. The adjusted beam which projects a circle is shaped into an annular beam which projects a circular ring and is outputted, so that the diameter of the adjusted beam is the same as the outer diameter of the metal coating or the hole diameter of the drill hole. The projection of the annular beam is exactly the same as the cross section of the metal coating on the wall of the drill hole, so that the annular beam covers the metal coating on the cross section and ablates the material, thereby avoiding damaging the hole wall and improving the situation that the metal coating is not completely removed. In addition, the annular beam dynamic focusing module also refracts a branch beam from the annular beam, and projects the branch beam onto the corresponding monitoring equipment. The diameter of the branch beam and the change of the laser energy can be monitored to monitor the diameter of the annular beam and the change of the laser energy during the removal of the metal coating. When the diameter of the branch beam and / or the change of the laser energy monitored in real time exceeds the preset range, it is determined that the focal point of the current annular beam needs to be adjusted. The feedback adjustment mechanism of the beam energy and the beam diameter can be established through this monitoring method to ensure that the processing energy is stable and the diameter of the beam is equal to the outer diameter of the metal coating or the hole diameter of the drill hole. The three-dimensional offset module is used to manipulate the annular beam dynamic focusing module for adjustment. The system avoids the situation that the annular beam is located inside the drill hole and is difficult to observe, and the energy and diameter of the annular beam cannot be adjusted in time, resulting in insufficient material removal at the focal point, or the removal diameter is too small or too large.

[0030] The beam diameter and divergence angle dynamic control module is a key module for realizing the shaping of the laser beam outer contour, which is composed of an expander mirror group and an expander mirror switcher. The expander mirror group includes a plurality of expander mirrors with different expansion ratios. Each expander mirror placed in the laser path will amplify the laser beam. After obtaining the drill hole diameter or according to the outer diameter data of the metal coating, the target diameter value is obtained. According to the multiple ratio of the diameter value of the initial beam and the target diameter value, the expander mirror with the appropriate ratio is selected, and the selected expander mirror is placed in the laser path by the expander mirror switcher, so as to adjust the diameter of the initial beam by expansion, and output the adjusted beam with a specified multiple ratio of the ring width of the target annular beam.

[0031] The structure for realizing the secondary shaped laser beam in the annular beam dynamic focusing module comprises a telecentric focusing field mirror, an annular beam shaper group and a mirror group switcher. The annular beam shaper group is also composed of annular beam shapers of various sizes and models, and the circular projection of the adjusted light beam is modified into a circular ring shape by calling the matched annular beam shaper through the mirror group switcher, as shown in FIG. 2, to output an annular beam. Then the telecentric focusing field mirror is used for focusing and adjusting, as shown in FIG. 3, so that the energy of the annular beam is focused at the focal point to enhance the removal effect of the laser on the metal coating. The telecentric focusing field mirror adjusts the focal point position of the annular beam along the axial direction of the laser path by changing the distance between the telecentric focusing field mirror and the annular beam shaper. The shaped annular beam can be used as a laser beam for removing redundant parts of the metal coating.

[0032] The structure for realizing the split branch beam in the annular beam dynamic focusing module comprises a beam splitter and an energy distribution detector. The beam splitter is arranged on the laser path to transmit part of the annular beam and refract another part of the annular beam at a specific angle to deviate from the original laser path to generate a branch light path. In this embodiment, the energy and diameter of the annular beam transmitted by the beam splitter are equal to those of the branch beam refracted out, and the branch beam is projected on the receiving end of the energy distribution detector, so that the energy and diameter of the annular beam in the hole can be obtained by measuring the laser energy and diameter of the branch beam.

[0033] Based on the above embodiment, in order to realize the distance between the telecentric focusing field mirror and the annular beam shaper, the focal point three-dimensional offset module comprises a scanning galvanometer and a three-dimensional motion guide rail. The scanning galvanometer is a high-precision sub-controller widely used in laser processing control systems. After obtaining the branch beam data transmitted by the energy distribution detector, the scanning galvanometer serves as the core of feedback response to control the relative movement of the telecentric focusing field mirror and the annular beam shaper installed on the three-dimensional motion guide rail, so as to fine-tune the distance between the two to change the focal point position.

[0034] Based on the above embodiment, in order to adjust the collimation of the initial light beam, a beam collimation module is also arranged on the laser path between the laser generation module and the beam diameter and divergence angle dynamic control module to collimate the laser line generated by the laser generation module before transmitting it to the beam diameter and divergence angle dynamic control module.

[0035] Since multiple modules need to cooperate in the laser processing system of the above embodiment to better play their roles, in order to reduce the operation difficulty and improve the system reliability, a control center is added in the processing system as the core of integrated control in an embodiment. The multiple modules are connected to the control center to realize data interconnection, and the control center sends instructions to coordinate the cooperation of the multiple modules.

[0036] In general, if the energy intensity of the laser beam is adjusted so that the focal point of the annular beam is close to the energy required to ablate the metal plating layer, the focal point of the annular beam can be moved to the surface of the non-drillable layer without damaging the non-drillable layer by precise control, thereby completely removing the stub. However, if the energy difference is too small, the ablation speed is slow and the efficiency is extremely low. In order to increase production capacity and reduce costs, a higher energy laser beam must be used for processing, which will cause the off-focus radiation zone around the focal point of the annular beam to extend to the non-drillable layer with sufficient energy to ablate the stub. In order to avoid damaging the non-drillable layer, a distance between the focal point of the annular beam and the non-drillable layer is required to be reserved so that the off-focus radiation zone does not contact the non-drillable layer, and the stub in this section is ablated and removed by the off-focus radiation zone.

[0037] The embodiment discloses a laser processing method for a hole wall metal plating layer, as shown in FIG. 4, which is suitable for the laser processing system in the foregoing embodiment, and includes the following steps:

[0038] Step one: measure the position coordinates, diameter and depth of the drill hole, detect the depth coordinates of the non-drillable layer, and the thickness and cross-sectional shape of the metal plating layer, and input the above data into the control center;

[0039] Step two: after the preparation work is completed, the control center starts the laser generation module (laser generator) to generate an initial light beam, adjusts the laser path according to the position coordinates of the drill hole, so that the light spot of the initial light beam projected on the printed circuit board covers the drill hole;

[0040] Step three: adjust the collimation of the initial light beam through the light beam diameter and divergence angle dynamic control module, and then adjust the divergence angle of the initial light beam, output a controlled laser beam with a diameter matched with the thickness of the metal plating layer, i.e., the adjusted light beam;

[0041] Step four: the annular light beam is output by the annular light beam dynamic focusing module according to the cross-sectional shape and thickness of the metal plating layer, and the cross-sectional shape of the metal plating layer, the thickness of the metal plating layer and the diameter of the drill hole are matched;

[0042] Step five: a part of the annular light beam is extracted to form a branch light beam by the annular light beam dynamic focusing module, and the branch light beam is monitored at least one of the following: laser energy monitoring, and light beam diameter monitoring;

[0043] The laser energy monitoring of the branch light beam includes: the monitoring branch light beam laser energy is converted into the monitoring annular light beam laser energy by adjusting the branch light beam and the annular light beam in a proportional manner;

[0044] When the laser energy of the annular light beam is less than 90% of the calibration energy, the focal point position of the annular light beam is adjusted so that the percentage of the laser energy of the annular light beam to the calibration energy is between 90% and 100%;

[0045] Wherein, the diameter monitoring of the branch light beam comprises: monitoring the diameter of the annular light beam synchronously by monitoring the diameter change of the branch light beam in the way of adjusting the branch light beam and the annular light beam proportionally;

[0046] When the deviation of the diameter of the annular light beam from the hole diameter of the drilling hole exceeds ±10%, the focal point position of the annular light beam is adjusted so that the deviation is less than or equal to 10%;

[0047] Step six: according to the depth coordinates of the non-drillable layer and the depth of the drilling hole, the moving distance of the focal point of the annular light beam is limited to be less than the depth of the drilling hole until the residual pile removal is completed.

[0048] In step six, in the case that the laser energy is increased to improve the overall efficiency, as shown in FIG. 5, the last part of the residual pile close to the non-drillable layer needs to be ablated by using the defocused radiation zone of the annular light beam, at this time, the energy of the defocused radiation zone is lower than that of the focal point area, so when the edge of the defocused radiation zone reaches the non-drillable layer, the focal point is stopped adjusting and kept for a preset time, so that the defocused radiation zone has sufficient time to ablate the residual pile. For example, the distance between the focal point of the annular light beam and the non-drillable layer can be controlled to be the focal depth of the annular light beam, the focal point of the annular light beam is stopped moving, so that the defocused range of the annular light beam can just remove the remaining metal plating layer without damaging the non-drillable layer, thereby improving the accuracy of laser removal of the residual pile.

[0049] The embodiment of the present application provides a laser processing system, comprising a laser generating module, a beam diameter and divergence angle dynamic control module, an annular light beam dynamic focusing module and a focal point three-dimensional offset module arranged on the same laser path;

[0050] The laser generating module is arranged to generate an initial light beam;

[0051] The beam diameter and divergence angle dynamic control module is arranged to adjust the diameter and divergence angle of the initial light beam to form an adjusted light beam with a diameter matching the thickness of the metal plating layer in proportion;

[0052] The annular light beam dynamic focusing module is arranged to shape the adjusted light beam into an annular light beam matching the cross-sectional shape of the metal plating layer, and refract a branch light beam, and by monitoring the laser energy and the beam diameter of the branch light beam, the dynamic parameters of the laser energy and the beam diameter of the annular light beam are obtained;

[0053] The focal point three-dimensional offset module is arranged to dynamically adjust the focal point of the annular light beam according to the laser energy and the beam diameter of the annular light beam and the depth of the non-drillable layer.

[0054] The light beam diameter and divergence angle dynamic control module comprises a beam expander group and a beam expander switcher arranged on the laser path, the beam expander group is composed of beam expanders with multiple expansion ratios, and the beam expander switcher is arranged to output adjustment beams with different diameters by switching beam expanders with different expansion ratios.

[0055] The annular light beam dynamic focusing module comprises a telecentric focusing field lens, an annular light beam shaper group and a lens group switcher, the lens group switcher is arranged to switch the annular light beam shaper to output annular light beams with different diameters, and the telecentric focusing field lens is arranged to shape and focus the annular light beam.

[0056] The annular light beam dynamic focusing module further comprises a beam splitter and an energy distribution detector, the energy distribution detector is arranged on the side of the laser path, the beam splitter is arranged on the laser path and is arranged to refract a part of the annular light beam to form a branch light beam and project the branch light beam to the receiving end of the energy distribution detector, and the energy distribution detector is arranged to dynamically monitor the laser energy and the beam diameter of the annular light beam.

[0057] The focal point three-dimensional offset module comprises a scanning galvanometer and a three-dimensional motion guide rail; the telecentric focusing field lens and the annular light beam shaper are respectively slidably installed on the three-dimensional motion guide rail; the scanning galvanometer is in data intercommunication with the energy distribution detector, and controls the distance between the telecentric focusing field lens and the annular light beam shaper to adjust the focal point position of the annular light beam.

[0058] The laser processing system further comprises a beam collimation module, the beam collimation module is arranged on the laser path between the laser generation module and the light beam diameter and divergence angle dynamic control module, and the beam collimation module is arranged to adjust the collimation of the initial light beam.

[0059] The laser processing system further comprises a control center, the laser generation module, the light beam diameter and divergence angle dynamic control module, the annular light beam dynamic focusing module and the focal point three-dimensional offset module are respectively in communication connection with the control center, and the control center is provided with laser parameters and printed circuit board processing parameters to cooperatively control the operation of the multiple modules.

[0060] The control center pre-stores depth coordinate data of the non-drillable layer, and the control center instructs the annular light beam dynamic focusing module and the focal point three-dimensional offset module to adjust the minimum distance between the focal point of the annular light beam and the non-drillable layer to be greater than the maximum radius of the out-of-focus radiation area of the annular light beam.

[0061] The embodiment of the present application also provides a hole wall metal coating laser processing method, which is applied to the laser processing system as described above, and the method comprises the following steps:

[0062] Step 1: measuring the position coordinates, diameter and depth of the drill hole, detecting the depth coordinates of the non-drillable layer, and detecting the thickness and cross-sectional shape of the metal coating layer;

[0063] Step two: start the laser generating module to generate an initial light beam, and adjust the laser path according to the position coordinates of the drill hole, so that the light spot of the initial light beam projected on the printed circuit board covers the drill hole;

[0064] Step three: adjust the diameter and divergence angle of the initial light beam through the light beam diameter and divergence angle dynamic control module, and output an adjusted light beam with a diameter proportional to the thickness of the metal plating layer;

[0065] Step four: according to the cross-sectional shape of the metal plating layer and the thickness of the metal plating layer, the adjusted light beam is reshaped by the annular light beam dynamic focusing module, and an annular light beam matching the cross-sectional shape of the metal plating layer, the thickness of the metal plating layer, and the diameter of the drill hole is outputted;

[0066] Step five: through the annular light beam dynamic focusing module, a part of the annular light beam is extracted to form a branch light beam, and the branch light beam is monitored at least one of the following: laser energy monitoring, and light beam diameter monitoring;

[0067] Wherein, the laser energy monitoring of the branch light beam includes: through the isometric adjustment of the branch light beam and the annular light beam, the laser energy monitoring of the branch light beam is converted into the laser energy monitoring of the annular light beam; in response to determining that the laser energy of the annular light beam is lower than 90% of the calibration energy, adjusting the focal point position of the annular light beam so that the percentage of the laser energy of the annular light beam to the calibration energy is between 90% and 100%;

[0068] Wherein, the light beam diameter monitoring of the branch light beam includes: through the isometric adjustment of the branch light beam and the annular light beam, the diameter change of the branch light beam is monitored to synchronously monitor the diameter of the annular light beam; in response to determining that the diameter deviation of the annular light beam from the hole diameter of the drill hole exceeds ±10%, adjusting the focal point position of the annular light beam so that the deviation is less than or equal to 10%;

[0069] Wherein, the calibration energy is the input laser processing energy value.

[0070] Step six: according to the depth coordinates of the non-drillable layer and the depth of the drill hole, limit the moving distance of the focal point of the annular light beam to be less than the depth of the drill hole, until the residual stub removal is completed.

[0071] According to the depth coordinates of the non-drillable layer and the depth of the drill hole, limit the moving distance of the focal point of the annular light beam to be less than the depth of the drill hole, until the residual stub removal is completed, including:

[0072] When the defocus radiation area edge of the annular light beam reaches the non-drillable layer, stop adjusting the focal point and keep for a preset time, and the residual stub removal is completed.

[0073] The laser processing system of the present application is to process the redundant part of the metal plating layer by replacing the mechanical drilling process with laser processing. By utilizing the plasticity of laser, the laser is shaped into a ring shape matching the cross-sectional shape of the metal plating layer, forming a cylindrical removal zone to remove the redundant metal plating layer along the drilling axis. When reaching the non-drillable layer, the cylindrical removal zone of the ring laser has a better edge shaping effect than the inverted conical cutting zone of the drilling process, that is, the ring laser can remove the redundant metal plating layer closer to the non-drillable layer, thereby reducing the stub or even completely cleaning up the stub. In order to overcome the technical barrier of difficult control of the focal point in laser processing, the processing system provides a focal point dynamic adjustment function specially used for precise removal of the stub, which can maximize the removal of the stub while ensuring the integrity of the non-drillable layer, thereby greatly improving the performance of the printed circuit board for high-speed transmission purposes.

[0074] The processing method of the present application also provides adaptive adjustment of the focal point of the ring beam according to the drilling and the thickness of the metal plating layer in the drilling as the laser ablation continuously deepens the drilling. By this method, the focal point position of the ring beam can be accurately controlled, the stub can be precisely ablated, and damage to the hole wall and the non-drillable layer of the drilling can be avoided, thereby ensuring the yield of high-performance printed circuit boards and reducing costs.

Claims

1. A laser processing system, comprising a laser generating module, a beam diameter and divergence angle dynamic control module, a ring beam dynamic focusing module and a focal point three-dimensional offset module arranged on the same laser path; the laser generating module is arranged to generate an initial beam; the beam diameter and divergence angle dynamic control module is arranged to adjust the diameter and divergence angle of the initial beam to form an adjusted beam with a diameter matching the thickness of a metal coating layer; the ring beam dynamic focusing module is arranged to shape the adjusted beam into a ring beam matching the cross-sectional shape of the metal coating layer and refract a branch beam, and by monitoring the laser energy and beam diameter of the branch beam, the dynamic parameters of the laser energy and beam diameter of the ring beam are obtained; the focal point three-dimensional offset module is arranged to dynamically adjust the focal point of the ring beam according to the laser energy and beam diameter of the ring beam and the depth of the non-drillable layer.

2. The laser processing system of claim 1, wherein, the beam diameter and divergence angle dynamic control module comprises an expander mirror group and an expander mirror switch arranged on the laser path, the expander mirror group is composed of expander mirrors with different expansion ratios, and the expander mirror switch is arranged to output adjusted beams with different diameters by switching expander mirrors with different expansion ratios.

3. The laser processing system of claim 1, wherein, the ring beam dynamic focusing module comprises a telecentric focusing field mirror, a ring beam shaper group and a mirror group switch, the mirror group switch is arranged to switch the ring beam shaper to output ring beams with different diameters, and the telecentric focusing field mirror is arranged to shape and focus the ring beam.

4. The laser processing system of claim 3, wherein, the ring beam dynamic focusing module further comprises a beam splitter and an energy distribution detector, the energy distribution detector is arranged on the side of the laser path, the beam splitter is arranged on the laser path and is arranged to refract a part of the ring beam to form the branch beam and project the branch beam to the receiving end of the energy distribution detector, and the energy distribution detector is arranged to dynamically monitor the laser energy and the beam diameter of the ring beam.

5. The laser processing system of claim 4, wherein, the focal point three-dimensional offset module comprises a scanning galvanometer and a three-dimensional motion guide rail; the telecentric focusing field mirror and the ring beam shaper are respectively slidingly installed on the three-dimensional motion guide rail; the scanning galvanometer and the energy distribution detector are data-intercommunicated, and the distance between the telecentric focusing field mirror and the ring beam shaper is controlled by the scanning galvanometer to adjust the focal point position of the ring beam. 6.The laser processing system of claim 1, further comprising a beam collimation module arranged on the laser path between the laser generating module and the beam diameter and divergence angle dynamic control module, the beam collimation module is arranged to adjust the collimation of the initial beam. 7.The laser processing system of claim 1, further comprising a control center, the laser generating module, the beam diameter and divergence angle dynamic control module, the ring beam dynamic focusing module and the focal point three-dimensional offset module are respectively communicatively connected with the control center, and the control center is provided with laser parameters and printed circuit board processing parameters to cooperatively control the operation of the modules.

8. The laser processing system of claim 7, wherein, The control center pre-stores depth coordinate data of the non-drillable layer, and instructs the annular light beam dynamic focusing module and the focal point three-dimensional offset module to adjust the minimum distance between the focal point of the annular light beam and the non-drillable layer to be greater than the maximum radius of the defocus radiation area of the annular light beam.

9. A method for laser processing of a hole wall metal plating layer, applied to the laser processing system of any one of claims 1-8, the method comprising: measuring the position coordinates, diameter and depth of the drill hole, detecting the depth coordinates of the non-drillable layer, and detecting the thickness and cross-sectional shape of the metal plating layer; starting the laser generation module to generate an initial light beam, and adjusting the laser path according to the position coordinates of the drill hole so that the initial light beam projects a light spot on the printed circuit board covering the drill hole; adjusting the diameter and divergence angle of the initial light beam by the light beam diameter and divergence angle dynamic control module, and outputting an adjusted light beam with a diameter matching the thickness of the metal plating layer in proportion; reshaping the adjusted light beam according to the cross-sectional shape of the metal plating layer and the thickness of the metal plating layer by the annular light beam dynamic focusing module, and outputting an annular light beam matching the cross-sectional shape of the metal plating layer, the thickness of the metal plating layer, and the diameter of the drill hole; extracting a part of the annular light beam to form a branch light beam by the annular light beam dynamic focusing module, and monitoring the branch light beam at least one of: laser energy monitoring, and light beam diameter monitoring; wherein the laser energy monitoring of the branch light beam comprises: converting the laser energy monitoring of the branch light beam into the laser energy monitoring of the annular light beam by isometrically adjusting the branch light beam and the annular light beam; and in response to determining that the laser energy of the annular light beam is less than 90% of the calibrated energy, adjusting the focal point position of the annular light beam so that the percentage of the laser energy of the annular light beam to the calibrated energy is between 90% and 100%; wherein the light beam diameter monitoring of the branch light beam comprises: monitoring the diameter of the annular light beam synchronously by monitoring the diameter change of the branch light beam by isometrically adjusting the branch light beam and the annular light beam; and in response to determining that the diameter deviation of the annular light beam from the hole diameter of the drill hole exceeds ±10%, adjusting the focal point position of the annular light beam so that the deviation is less than or equal to 10%; limiting the movement distance of the focal point of the annular light beam to be less than the depth of the drill hole according to the depth coordinates of the non-drillable layer and the depth of the drill hole until the residual stub removal is completed.

10. The laser processing method of a hole wall metal plating layer according to claim 9, wherein, The limiting the movement distance of the focal point of the annular light beam to be less than the depth of the drill hole according to the depth coordinates of the non-drillable layer and the depth of the drill hole until the residual stub removal is completed comprises: stopping adjusting the focal point when the edge of the defocus radiation area of the annular light beam reaches the non-drillable layer, and keeping for a preset time, and the residual stub removal is completed.

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