Micro blind hole machining method and ultrafast laser machining equipment

Abstract

The invention discloses a micro blind hole machining method and ultrafast laser machining equipment, the ultrafast laser machining equipment comprises an ultrafast laser and a galvanometer assembly, and the machining method comprises the steps that the focusing position of the galvanometer assembly is adjusted; the ultrafast laser is controlled to emit a short pulse laser beam with first machining power, the short pulse laser beam is focused to a first machining point on the HDI plate to be machined through the galvanometer assembly, rough machining is conducted according to first machining duration, and a first rough drilled hole is obtained; and the ultrafast laser is controlled to emit a short pulse laser beam with second machining power, the short pulse laser beam advances along the same light path as the short pulse laser beam with the first machining power, the short pulse laser beam is focused to the first coarse drilling hole through the galvanometer assembly, fine machining is carried out according to second machining duration, and a first micro blind hole is obtained. According to the invention, the machining roundness of the micro blind hole is ensured, the alignment precision of the whole equipment is improved, and the machining efficiency is improved.

Description

[0001] This application is a divisional application of a Chinese patent application filed on 2021 year 01 month 19 day, with the application number: 202110070626.X , and the invention name is " Based on Multi-axis micro-blind hole processing method and system based on ultrafast laser ". Technical Field

[0002] The present invention relates to the field of laser processing, and particularly to a method for processing micro blind holes and an ultrafast laser processing device. Background Art

[0003] With the development of communication technology and the application of the Internet of Things, people's demand for the speed and efficiency of information exchange has been greatly improved. Therefore, the high-density interconnection of circuit boards has become a new application direction. As such, there are higher requirements for reducing the drilling aperture and the hole pitch of laser processing. In the prior art, there are bottlenecks in laser processing drilling. For example, for laser processing of blind holes, the blind holes after laser processing drilling in the prior art often have the following problems: The blind holes that can be laser processed in the prior art are usually above 100 microns, and the processing speed is slow, resulting in low processing efficiency; at the same time, the laser processing quality of the blind holes is poor, and there are usually phenomena such as copper spattering on the surface, molten balls and protrusions of glass fibers on the hole wall, residual glue and bottom side etching at the hole bottom, copper hanging and peeling at the hole opening (such as the schematic diagram of the blind hole processed in the prior art shown in the rightmost column of Figure 4 ), and there are also thermal effect problems. Summary of the Invention

[0004] Based on this, it is necessary to provide a method for processing micro blind holes and an ultrafast laser processing device for the above technical problems to solve problems such as low processing efficiency and poor processing quality.

[0005] A multi-axis micro blind hole processing method is applied to an ultrafast laser processing device. The ultrafast laser processing device includes an ultrafast laser and a galvanometer assembly. The processing method includes: Adjust the focusing position of the galvanometer assembly; control the ultrafast laser to emit a short-pulse laser beam with a first processing power, and focus it to a first processing point on the HDI board to be processed through the galvanometer assembly, and perform rough processing for a first processing duration to obtain a first rough drill hole; Control the ultrafast laser to emit a short-pulse laser beam with a second processing power, travel along the same optical path as the short-pulse laser beam with the first processing power, and focus it to the first rough drill hole through the galvanometer assembly, and perform fine processing for a second processing duration to obtain a first micro blind hole; Among them, the first processing power is greater than the second processing power, the second processing duration is greater than the first processing duration, the first processing duration is proportional to the number of laser pulses received by the corresponding first processing point in the rough processing stage, and the second processing duration is proportional to the number of laser pulses received by the corresponding first processing point in the fine processing stage.

[0006] Optionally, the HDI board to be processed includes a surface copper layer, a glass fiber glue layer, and a bottom copper layer connected in sequence, and the bottom surfaces of the first rough drill hole and the first micro blind hole are the top surface of the bottom copper layer; The hole shape of the first rough drill hole is perfected by a short-pulse laser beam with the second processing power to obtain the first micro blind hole.

[0007] Optionally, the ultrafast laser is a picosecond green laser.

[0008] Optionally, the diameter of the hole to be processed is 20-60 μm.

[0009] Optionally, the short-pulse laser beam emitted by the ultrafast laser is a short-pulse laser beam with a Gaussian distribution; The processing method further includes: Shaping the short-pulse laser beam with a Gaussian distribution into a quasi-flat-top laser beam by a shaping component; Performing beam splitting on the quasi-flat-top laser beam by a beam splitting component; Focusing at least two split beamlets separated by the beam splitting component by a galvanometer component respectively.

[0010] Optionally, the performing beam splitting on the quasi-flat-top laser beam by the beam splitting component includes: Dividing the short-pulse laser beam with the first processing power into at least two beamlets by the beam splitting component to perform rough processing with the first processing duration on at least two first processing points to obtain at least two first rough drill holes; Dividing the short-pulse laser beam with the second processing power into at least two beamlets by the beam splitting component to perform fine processing with the second processing duration on at least two of the first rough drill holes to obtain at least two first micro blind holes.

[0011] Optionally, after performing beam splitting on the quasi-flat-top laser beam by the beam splitting component, it further includes: Controlling the output powers of at least two split beamlets separated by the beam splitting component to be equal by a power control component.

[0012] Optionally, the processing method further includes: Travel to the second processing point on the to-be-processed HDI board according to a preset movement path; wherein, the micro blind vias on one preset movement path have the same to-be-processed hole diameter; Focus at least two of the split light beams corresponding to the first processing power through the galvanometer assembly, and perform rough processing on at least two of the second processing points for the first processing duration to obtain at least two second rough drill holes; Along the optical path of the split light beam of the first processing power, perform fine processing on at least two of the second rough drill holes through at least two of the split light beams corresponding to the second processing power to obtain at least two second micro blind vias.

[0013] An ultrafast laser processing device includes an ultrafast laser, a galvanometer assembly, and a control module, and the control module is connected to the ultrafast laser and the galvanometer assembly; the control module is used to execute the micro blind via processing method described above.

[0014] Optionally, it further includes a frame with a movable moving platform; the ultrafast laser, the galvanometer assembly, and the control module are all installed on the frame; the to-be-processed HDI board is installed on the moving platform.

[0015] The above blind hole processing method can, after the galvanometer assembly performs one-time scanning alignment and focusing, obtain multiple (at least two) split light beams by splitting the laser beam corresponding to the first processing power, and successively complete the rough machining of multiple (at least two) first rough drill holes and the fine machining of multiple (at least two) first micro blind holes. During this processing process, first, it is ensured that the entire above-mentioned processing process can be completed based on the one-time scanning alignment and focusing of the galvanometer assembly (during the entire processing process, the galvanometer assembly, the focal position after focusing, and the first processing point do not need to be moved or adjusted, and only the laser power needs to be changed through the power adjustment assembly). Second, it is ensured that rough machining and fine machining are respectively completed by laser beams with different powers (the first processing power and the second processing power) (during the fine machining process, the first rough drill holes obtained by rough machining are further improved and decorated to make the micro blind hole processing effect better, and since there is no position accuracy error caused by secondary repeated alignment during the rough machining and fine machining processes, the machining roundness is ensured and the overall alignment accuracy of the equipment is improved); the simultaneous existence of the above two guarantee conditions makes the finally obtained first micro blind holes free from obvious surface copper splashing, glass fiber melting balls and glass fiber protrusions on the hole wall, residual glue and bottom side etching at the hole bottom, copper hanging and peeling at the hole opening, etc., having a good hole opening effect, and at the same time the thermal effect is smaller. And precisely because the galvanometer assembly can complete the entire above-mentioned processing process based on one-time scanning alignment and focusing, the speed of processing micro blind holes is greatly improved (the one-time adjustment process of the galvanometer assembly takes about 360 microseconds, but the entire above-mentioned processing process of multiple first micro blind holes is only 120 microseconds in total); and the present invention further improves the processing speed and processing efficiency by simultaneously performing laser processing of multiple first micro blind holes with multiple split light beams. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings without creative efforts based on these drawings.

[0017] Figure 1 It is a flowchart of a multi-axis micro blind hole processing method based on ultrafast laser in an embodiment of the present invention.

[0018] Figure 2 It is a structural schematic diagram of a multi-axis micro blind hole processing system based on ultrafast laser in an embodiment of the present invention.

[0019] Figure 3 It is a principle block diagram of a multi-axis micro blind hole processing system based on ultrafast laser in an embodiment of the present invention.

[0020] Figure 4 It is a comparison schematic diagram of the micro blind holes processed by the multi-axis micro blind hole processing method based on ultrafast laser in an embodiment of the present invention and the blind holes processed in the prior art.

[0021] The reference numerals in the specification are as follows: 1. Ultrafast laser; 2. Power adjustment component; 3. Shaping component; 4. Beam splitting component; 5. Beam expanding component; 6. Galvo component; 61. Galvo; 62. Focusing lens; 7. Control module. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] The multi-axis micro blind hole processing method based on ultrafast laser provided in this embodiment provides a multi-axis micro blind hole processing method based on ultrafast laser, including the following steps: S10. Receive a laser processing instruction, obtain a first processing power, a first processing duration, and a to-be-processed hole diameter from the laser processing instruction, and control the ultrafast laser 1 to emit a pulsed laser beam with a Gaussian distribution having the first processing power (the energy of the Gaussian spot in the Gaussian-distributed laser beam is distributed in a Gaussian manner by line); wherein, the laser processing instruction contains the processing parameters of the current laser processing, such as the first processing power, the first processing duration, the to-be-processed hole diameter, and the preset moving path, the second processing power, and the second processing duration mentioned later, etc.; the laser processing instruction can be generated by triggering a preset button after the to-be-processed HDI (High Density Interconnector) board is installed on the moving platform of the rack. In the present invention, a short-pulse laser beam with a very high power density can conduct a huge amount of energy greater than the material ablation energy threshold to the to-be-processed HDI board in a short time, causing the processing points (such as the first processing point and the second processing point mentioned later) of the to-be-processed HDI board to be melted and evaporated. At the same time, during the evaporation process, the material volume in the hole expands rapidly, generating a large vapor pressure, which can push the melted workpiece material out of the hole. And the processing time of the focal point (such as the first processing time and the second processing time, etc.) determines the number of laser pulses received by the processing point on the surface of the to-be-processed HDI board. Among them, the more accumulated pulses, the more accumulated energy, and thus the more material is melted and evaporated. Optionally, the to-be-processed HDI board includes a surface copper layer, a glass fiber adhesive layer, and a bottom copper layer connected in sequence. The micro blind holes (including the first micro blind hole and the second micro blind hole mentioned later, etc.) only need to be formed on the surface copper layer and the glass fiber adhesive layer.

[0024] In an embodiment, the to-be-processed hole diameter is 20 - 60 μm, that is, in the present invention, the diameter of the micro blind hole that can be finally processed is equal to the to-be-processed hole diameter shown. It can be understood that in the present invention, after starting the processing, first, the control module of the multi-axis micro blind hole processing system based on ultrafast laser controls the ultrafast laser 1 to emit a laser beam with the first processing power to prepare to enter the rough processing stage.

[0025] S20, control the shaping component 3 to shape the laser beam into a quasi-top-hat laser beam. Understandably, in a Gaussian-distributed laser beam, the area of the spot vertex is small, that is, the energy at the exact center of the spot is the largest, and the peak power density is high. There is a risk that the high energy at the center of the spot may damage the micro-blind vias (the bottom copper layer) of the HDI board to be processed. At the same time, if the energy at the edge of the Gaussian spot is weaker, it may not meet the required upper and lower aperture ratios for the electroplating process of the HDI board to be processed. In the present invention, after the shaping component 3 is set in the optical path, when the laser beam is shaped into a quasi-top-hat laser beam and then focused, the energy distribution of the focused spot is evenly processed, forming a quasi-top-hat laser beam with uniform energy and steep boundaries, making the bottom of the micro-blind vias more uniform, broadening the laser processing threshold, and at the same time avoiding the risk of ablation of the bottom copper layer due to excessive energy at the center of the laser focused spot.

[0026] S30, control the beam splitting component 4 to perform beam splitting on the quasi-top-hat laser beam. After splitting the laser beam into at least two split beams, control the output power of at least two split beams to be equal through the power adjustment component. In the present invention, it is necessary to split the laser beam into at least two (for example, two, three, four, etc.) split beams, and balance the power of each split beam through the power adjustment component 2, that is, make the output power (energy) of each split beam equal, so that multiple first micro-blind vias obtained by laser processing all have the same size and depth dimensions, etc. Refer to Figure 3 , Figure 3 After beam splitting through the beam splitting component 4 in, the laser beam is split into two split beams with equal energy.

[0027] Among them, the power adjustment component 2 can be a glass sheet motor that can balance and adjust the output power of the laser beam. For example: when the first processing power is 20W, and the beam splitting component 4 splits the quasi-top-hat laser beam into one split beam of 9W and one split beam of 11W (a total of two beams), at this time, the power adjustment component 2 needs to balance the power of the two split beams and make them become two split beams with a power of 10W each.

[0028] S40, obtain the beam diameter corresponding to the aperture to be processed, and control the beam expander component 5 to adjust the diameters of at least two split beams to the beam diameter. Understandably, after beam splitting, it is also necessary to perform beam expansion or beam contraction processing (determine the processing method as beam expansion or beam contraction according to the aperture requirement) on the split beams, so that the finally adjusted split beams correspond to the aperture to be processed finally required, in order to finally process micro-blind vias with an aperture equal to the aperture to be processed.

[0029] S50. The at least two adjusted split light beams are respectively focused by the galvanometer assembly 6 onto at least two of the first processing points spaced apart on the HDI board to be processed, so that after rough processing for the first processing duration at positions corresponding to at least two of the first processing points by the at least two split light beams corresponding to the first processing power, at least two first rough drill holes are obtained. Understandably, the first rough drill holes are recessed in the surface copper layer and the glass fiber glue layer, and the bottom surface of the first rough drill hole is the top surface of the bottom copper layer. That is, the first rough drill hole is finally processed from the surface copper layer to the bottom copper layer without damaging the bottom copper layer.

[0030] In the present invention, as Figure 2 shown, the multi-axis micro blind hole processing system based on an ultrafast laser includes an ultrafast laser 1, a power adjustment assembly 2, a shaping assembly 3, a beam splitting assembly 4, a beam expanding assembly 5, a galvanometer assembly 6, and a frame having a movable moving platform; at least two processing axes are provided on the frame, and a beam expanding assembly 5 and a galvanometer assembly 6 (the galvanometer assembly 6 includes a galvanometer 61 for swinging the split light beam for scanning alignment and a focusing mirror 62 for focusing the split light beam on the processing point) are provided on each processing axis; and the ultrafast laser 1, the power adjustment assembly 2, the shaping assembly 3, and the beam splitting assembly 4 are all mounted on the frame, and each split light beam after splitting by the beam splitting assembly 4 is injected into each beam expanding assembly 5 in one-to-one correspondence. The HDI board to be processed is mounted on the moving platform. In an embodiment, before step S60, the relative movement between the processing axes on the frame and the moving platform has been controlled to align each processing axis with the HDI board to be processed, so that each laser spot after being finally focused by the focusing mirror 62 on each processing axis can irradiate each first processing point in one-to-one correspondence. Understandably, the multiple first rough drill holes after rough processing are spaced apart, and the spacing distance therebetween can be preset, and the spacing distance can be adjusted by aligning the processing axes and the moving platform, and can also be further adjusted by the galvanometer assembly 6.

[0031] S60. Obtain the second processing power and the second processing duration from the laser processing instruction, and adjust the output power of the laser beam emitted by the ultrafast laser 1 from the first processing power to the second processing power; the first processing power is less than the second processing power, and the second processing duration is greater than the first processing duration. Understandably, after obtaining the second processing power and the second processing duration and adjusting the output power of the laser beam to the second processing power, it represents entering the fine processing stage. The laser beam with the second processing power still passes through the same optical path as the laser beam with the first processing power, and after passing through the shaping component 3, the beam splitting component 4, the beam expanding component 5, the galvanometer component 6, etc. in sequence, it starts to irradiate the same first processing point in S70 for fine processing. Understandably, during the process of the laser beam with the second processing power passing through the above optical path, components such as the shaping component 3, the beam splitting component 4, the beam expanding component 5, and the galvanometer component 6 will not move or adjust at all. That is to say, the galvanometer component 6 only performs one scan alignment and focusing before rough processing and will not perform secondary scan alignment and focusing during the fine processing stage. Therefore, the laser beam with the first processing power corresponding to the rough processing stage and the laser beam with the second processing power corresponding to the fine processing stage irradiate the same first processing point through the same and completely unmoved optical path, eliminating the position accuracy error caused by secondary repeated alignment in the rough processing and fine processing processes and ensuring the processing roundness.

[0032] S70. Perform fine processing on at least two first rough drill holes for the second processing duration through at least two split light beams corresponding to the second processing power to obtain at least two first micro blind holes, and the aperture of the first micro blind hole is equal to the aperture to be processed. In one embodiment, the first micro blind hole is recessed in the surface copper layer and the glass fiber adhesive layer, and the bottom surface of the first micro blind hole is the top surface of the bottom copper layer. That is to say, the first micro blind hole is finally processed from the surface copper layer to the bottom copper layer without damaging the bottom copper layer.

[0033] In the present invention, the laser power used in the processing stage of rough processing to obtain the first rough drill hole is large (the first processing power), and the light emission time during the processing process is short (the first processing duration); on the contrary, the laser power used in the fine processing stage is small (the second processing power), and the light emission time during the processing process is long (the second processing duration); in this way, first, through the relatively high-power laser beam in the rough processing stage, the surface copper layer can be broken through to drill a hole with a size that meets the basic requirements and obtain the first rough drill hole that conforms to the basic hole shape; furthermore, through the relatively low-power and long light emission time laser beam in the fine processing stage, the hole shape can be further improved on the basis of the first rough drill hole obtained by rough processing to obtain the first micro blind hole, and the ratio of the bottom aperture to the top aperture of the first micro blind hole meets the preset aperture requirement (during the fine processing process, the first rough drill hole obtained by rough processing is further improved and decorated to make the processing effect of the micro blind hole better (such as Figure 4Schematic diagram of the micro-blind holes processed by the present invention shown in the left-middle column). And since there is no positional accuracy error caused by secondary repeated alignment in the rough machining and fine machining processes, the machining roundness (effect) is ensured, and the overall alignment accuracy of the equipment is improved.

[0034] Preferably, in the present invention, the ratio between the bottom hole diameter of the first micro-blind hole on the top surface of the bottom copper layer and the top hole diameter on the top surface of the surface copper layer is 0.8. In an embodiment, the first processing power is 10 - 30 w; the second processing power is 7 - 20 w. Further, the first processing duration is 30 - 100 μs, and the second processing duration is 60 - 150 μs. Under the above power and duration conditions, a first micro-blind hole with a hole diameter between 20 - 60 μm can finally be obtained.

[0035] Further, through practical operations, the preferred configuration values of the above parameters can be obtained as follows (when the surface copper layer is bright copper with a thickness of 1.5 μm and the fiberglass glue layer thickness is 25 μm): When the hole diameter to be processed is 20 μm, the first processing power is 12 W, the first processing duration is 30 μs; the second processing power is 8 W; the second processing duration is 60 μs; When the hole diameter to be processed is 30 μm, the first processing power is 16 W, the first processing duration is 50 μs; the second processing power is 12 W; the second processing duration is 90 μs; When the hole diameter to be processed is 40 μm, the first processing power is 18 W, the first processing duration is 70 μs; the second processing power is 14 W; the second processing duration is 110 μs; When the hole diameter to be processed is 50 μm, the first processing power is 20 W, the first processing duration is 80 μs; the second processing power is 15 W; the second processing duration is 120 μs; When the hole diameter to be processed is 60 μm, the first processing power is 22 W, the first processing duration is 100 μs; the second processing power is 16 W; the second processing duration is 140 μs.

[0036] The above-mentioned multi-axis micro-blind hole processing method and system based on ultrafast laser can, after the galvanometer assembly 6 performs one-time scanning alignment and focusing, obtain multiple (at least two) split light beams by splitting the laser beam corresponding to the first processing power, and successively complete the rough machining of multiple (at least two) first rough drill holes and the fine machining of multiple (at least two) first micro-blind holes. In this processing process, first, it is ensured that the entire above-mentioned processing process can be completed based on the one-time scanning alignment and focusing of the galvanometer assembly 6 (during the entire processing process, the galvanometer assembly 6, the focal position after focusing, and the first processing point do not need to be moved or adjusted, and only the laser power needs to be changed through the power adjustment assembly 2). Second, it is ensured that the rough machining and fine machining are respectively completed by laser beams with different powers (the first processing power and the second processing power) (during the fine machining process, the first rough drill holes obtained by rough machining are further improved and decorated, making the micro-blind hole processing effect better, and since there is no position accuracy error caused by secondary repeated alignment during the rough machining and fine machining processes, the machining roundness is ensured); the simultaneous existence of the above two guarantee conditions makes the finally obtained first micro-blind holes free from obvious surface copper spattering, glass fiber melting balls and glass fiber protrusions on the hole wall, residual glue and bottom side etching at the hole bottom, copper hanging and peeling at the hole opening, etc., having a good hole opening effect, and at the same time, the thermal effect is smaller. And precisely because the entire above-mentioned processing process can be completed based on the one-time scanning alignment and focusing of the galvanometer assembly 6, the speed of processing micro-blind holes is greatly improved (the one-time scanning alignment and focusing process of the galvanometer assembly 6 takes about 360 microseconds, but the entire above-mentioned rough machining and fine machining processes of multiple first micro-blind holes only take 120 microseconds); moreover, in the present invention, multiple first micro-blind holes are processed by multiple split light beams synchronously, further improving the processing speed and processing efficiency. In the actual practice process, the present invention can process about 1800 micro-blind holes per processing axis within 1 second. Since the present invention has at least two processing axes, actually at least 3600 micro-blind holes can be processed in 1 second.

[0037] Preferably, the ultrafast laser 1 is a picosecond green laser, and the wavelength of the laser beam emitted by the ultrafast laser 1 is 515 nm or 532 nm. The picosecond green laser has the characteristics of short pulse width and high peak power, resulting in a relatively high light absorption rate of the surface copper layer of the HDI board to be processed, eliminating the need for blackening or brownification pretreatment, saving the process, improving the drilling efficiency, and at the same time, due to the high peak power, reducing the thermal effect generated during the drilling process. At the same time, as an ultrafast laser, the picosecond green laser has strong flexibility in drilling hole diameters and can cooperate to finally obtain the 20 - 60 μm micro-blind holes in the present invention.

[0038] In an embodiment, after obtaining at least two first micro-blind holes, it further includes: Obtain a preset movement path from the laser processing instruction, control the relative movement of at least two of the split light beams and the HDI board to be processed according to the preset movement path, and focus at least two of the split light beams onto at least two second processing points arranged at intervals on the HDI board to be processed through a galvanometer assembly; Understandably, the above movement path can be set according to the number and arrangement of the micro blind holes actually required to be processed on the HDI board to be processed. One laser processing instruction corresponds to one preset movement path (and only micro blind holes with the same to-be-processed hole diameter are processed in this laser processing instruction). This preset movement path can correspond to the entire HDI board to be processed, or can also only correspond to a certain processing area in the HDI board to be processed. The first processing points are arranged at intervals, and the first processing points and the second processing points are also arranged at intervals. The controlling the relative movement of at least two of the split light beams and the HDI board to be processed according to the preset movement path specifically means that, according to the preset movement path, control the relative movement between the processing axis on the machine frame and the moving platform, so that each laser spot after the split light beams are scanned and aligned and focused through the galvanometer assemblies on the respective processing axes can irradiate on each second processing point one by one.

[0039] Adjust the output power of the laser beam emitted by the ultrafast laser 1 to the first processing power, and perform rough machining for the first processing duration at positions corresponding to at least two of the second processing points through at least two of the split light beams corresponding to the first processing power, to obtain at least two second rough drill holes; that is, after focusing the laser spot corresponding to the split light beam onto the second processing point, the control module adjusts the output power of the laser beam emitted by the ultrafast laser 1 to the first processing power to perform rough machining to obtain the second rough drill holes. Understandably, the second rough drill holes are recessed in the surface copper layer and the glass fiber adhesive layer, and the bottom surface of the second rough drill hole is the top surface of the bottom copper layer. That is, the second rough drill holes are finally processed from the surface copper layer to the bottom copper layer without damaging the bottom copper layer.

[0040] Adjust the output power of the laser beam emitted by the ultrafast laser 1 to the second processing power; understandably, after adjusting the output power of the laser beam to the second processing power, it means entering the fine processing stage. The laser beam with the second processing power still irradiates the second processing point for fine processing through the same optical path as the rough processing stage corresponding to the second rough drilling. Understandably, during the process of the laser beam with the second processing power passing through the above optical path, the shaping component 3, the beam splitting component 4, the beam expanding component 5, and the galvanometer component 6 will not move or adjust at all. That is, the galvanometer component 6 only performs one scan alignment and focusing before rough processing and will not perform secondary scan alignment and focusing during the fine processing stage. Therefore, the laser beam with the first processing power corresponding to the rough processing stage and the laser beam with the second processing power during the fine processing stage irradiate the same second processing point through the same and completely unmoved optical path, so that there is no position accuracy error caused by secondary repeated alignment during the rough processing and fine processing processes, ensuring the machining roundness.

[0041] Perform fine processing for a second processing duration on at least two second rough drill holes through at least two beam splitting light beams corresponding to the second processing power to obtain at least two second micro blind holes, and the aperture of the second micro blind holes is equal to the to-be-machined aperture. The second micro blind holes refer to micro blind holes with the same size and depth dimensions as the first micro blind holes. The second micro blind holes are recessed in the surface copper layer and the glass fiber glue layer, and the bottom surface of the second micro blind holes is the top surface of the bottom copper layer. That is, the second micro blind holes are finally processed from the surface copper layer to the bottom copper layer without damaging the bottom copper layer.

[0042] Understandably, in the present invention, after the preset movement path corresponding to the laser processing instruction travels to the last processing point and finishes processing the micro blind hole corresponding to this processing point, it automatically recognizes that the laser processing corresponding to this laser processing instruction has been completed. Otherwise, it will continue to move forward along the preset movement path and process micro blind holes at the corresponding positions of each processing point on the preset movement path.

[0043] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution is prior or subsequent. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0044] In one embodiment, a multi-axis micro blind hole processing system based on an ultrafast laser is provided. The multi-axis micro blind hole processing system based on an ultrafast laser corresponds one-to-one with the multi-axis micro blind hole processing method based on an ultrafast laser in the above embodiment. The multi-axis micro blind hole processing system based on an ultrafast laser includes an ultrafast laser 1, a power adjustment component 2, a shaping component 3, a beam splitting component 4, a beam expanding component 5, a galvanometer component 6, and a control module 7. The control module 7 is connected to the ultrafast laser 1, the power adjustment component 2, the shaping component 3, the beam splitting component 4, the beam expanding component 5, and the galvanometer component 6. The control module 7 is configured to execute the above multi-axis micro blind hole processing method based on an ultrafast laser. For the specific limitations of the control module 7 of the multi-axis micro blind hole processing system based on an ultrafast laser, reference can be made to the limitations of the multi-axis micro blind hole processing method based on an ultrafast laser in the foregoing text, which will not be elaborated herein. The above control module 7 can be implemented in whole or in part by software, hardware, and their combination. The above control module 7 can be embedded in or independent of the processor in a computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so as to facilitate the processor to call and execute the operations corresponding to the above respective modules.

[0045] In one embodiment, as Figure 2 and Figure 3 shown, the multi-axis micro blind hole processing system based on an ultrafast laser further includes a frame having a movable moving platform. The ultrafast laser 1, the power adjustment component 2, the shaping component 3, the beam splitting component 4, the beam expanding component 5, the galvanometer component 6, and the control module 7 are all mounted on the frame. The HDI board to be processed is mounted on the moving platform. Understandably, at least two processing axes are provided on the frame, and a beam expanding component 5 and a galvanometer component 6 are provided on each processing axis (the galvanometer component 6 includes a galvanometer 61 for swinging the split beam for scanning alignment and a focusing mirror 62 for focusing the split beam on the processing point). The ultrafast laser 1, the power adjustment component 2, the shaping component 3, and the beam splitting component 4 are all mounted on the frame, and the split beams after splitting by the beam splitting component 4 are respectively incident into the respective beam expanding components 5. The HDI board to be processed is mounted on the moving platform. It is possible to control the relative movement between the processing axes on the frame and the moving platform so that each processing axis is aligned with the HDI board to be processed, so that the laser spots after focusing of the split beams through the focusing mirrors 62 on each processing axis can respectively irradiate on each processing point.

[0046] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for machining micro blind holes, characterized in that, Applied to an ultrafast laser processing device, the ultrafast laser processing device includes an ultrafast laser and a galvanometer assembly, and the processing method includes: Adjust the focusing position of the galvanometer assembly; control the ultrafast laser to emit a short-pulse laser beam with a first processing power, and focus it onto a first processing point on the HDI board to be processed through the galvanometer assembly, and perform rough machining for a first processing duration to obtain a first rough drill hole; Control the ultrafast laser to emit a short-pulse laser beam with a second processing power, travel along the same optical path as the short-pulse laser beam with the first processing power, and focus it onto the first rough drill hole through the galvanometer assembly, and perform fine machining for a second processing duration to obtain a first micro blind hole; Wherein, the first processing power is greater than the second processing power, the second processing duration is greater than the first processing duration, the first processing duration is proportional to the number of laser pulses received by the corresponding first processing point in the rough machining stage, and the second processing duration is proportional to the number of laser pulses received by the corresponding first processing point in the fine machining stage.

2. The micro blind hole machining method according to claim 1, characterized in that, The first processing duration determines the number of laser pulses received by the corresponding first processing point in the rough machining stage, and the second processing duration determines the number of laser pulses received by the corresponding first processing point in the fine machining stage.

3. The micro blind hole machining method according to claim 1, characterized in that, The HDI board to be processed includes a surface copper layer, a glass fiber glue layer and a bottom copper layer connected in sequence, and the bottom surfaces of the first rough drill hole and the first micro blind hole are the top surface of the bottom copper layer; Improve the hole shape of the first rough drill hole through the short-pulse laser beam with the second processing power to obtain the first micro blind hole.

4. The micro blind hole processing method according to claim 1, characterized in that The ultrafast laser is a picosecond green laser.

5. The micro blind hole processing method according to claim 1, wherein The aperture to be processed is 20 - 60 μm.

6. The micro-blind hole processing method according to claim 1, characterized in that, The short-pulse laser beam emitted by the ultrafast laser is a short-pulse laser beam with a Gaussian distribution; The processing method further includes: Shape the short-pulse laser beam with a Gaussian distribution into a quasi-top-hat laser beam through a shaping component; Perform beam splitting processing on the quasi-top-hat laser beam through a beam splitting component; Focus at least two split beam splitting beams respectively through the galvanometer assembly.

7. The micro blind hole processing method according to claim 6, wherein, The performing beam splitting processing on the quasi-top-hat laser beam through the beam splitting component includes: Divide the short-pulse laser beam with the first processing power into at least two beams through the beam splitting component to perform rough machining for the first processing duration on at least two first processing points to obtain at least two first rough drill holes; Divide the short-pulse laser beam with the second processing power into at least two beams through the beam splitting component to perform fine machining for the second processing duration on at least two of the first rough drill holes to obtain at least two first micro blind holes.

8. The micro blind hole processing method according to claim 6, wherein, After performing beam splitting processing on the quasi-top-hat laser beam through the beam splitting component, it further includes: Control the output powers of at least two split beam splitting beams separated by the beam splitting component to be equal through a power control component.

9. The micro blind hole processing method according to claim 6, characterized in that, The processing method further includes: Travel to a second processing point on the HDI board to be processed according to a preset movement path; wherein, the micro blind holes on one preset movement path have the same aperture to be processed. Focus at least two of the split light beams corresponding to the first processing power through the galvanometer assembly, and perform rough processing on at least two of the second processing points for the first processing duration to obtain at least two second rough drill holes; Along the optical path of the split light beams of the first processing power, perform fine processing on at least two of the second rough drill holes through at least two of the split light beams corresponding to the second processing power to obtain at least two second micro blind holes.

10. An ultrafast laser processing device, characterized in that, It includes an ultrafast laser, a galvanometer assembly and a control module, and the control module is connected to the ultrafast laser and the galvanometer assembly; the control module is used to execute the micro blind hole processing method according to any one of claims 1 to 9.

11. The ultrafast laser processing device according to claim 10, characterized in that, It further includes a frame with a movable moving platform; the ultrafast laser, the galvanometer assembly and the control module are all installed on the frame; the HDI board to be processed is installed on the moving platform.

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