Laser drilling method and system

Abstract

The invention discloses a laser drilling method and system, and relates to the technical field of laser drilling. The laser drilling method comprises the steps that a pulse laser is used for drilling, and a micropore with the aperture ranging from 10 micrometers to 100 micrometers can be formed in a material to be machined by adjusting the waveform of a pulse string emitted by the pulse laser and shaping a light beam of the pulse string; the pulse string output frequency of the pulse laser is 1-20kHz, and the wavelength of the pulse string is 257-1064nm; the pulse string comprises at least two parts of sub-pulse waveforms, and according to the sequence, the sub-pulse energy in the front part of sub-pulse waveforms is larger than the sub-pulse energy in the rear part of sub-pulse waveforms. According to the drilling method, firstly, the high-energy pulse string is used for effectively removing the material, and then the low-energy pulse string is used for reducing damage to the bottom surface material. According to the laser drilling system, the pulse string light beams are shaped in the shaping system to achieve conversion of different light beams, and high-quality drilling with different hole diameters and high conicity can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser drilling, and in particular to a laser drilling method and system. Background Art

[0002] IC substrate is a subdivision of the PCB industry. It is mainly used to carry ICs. It has internal wiring to conduct signals between the chip and the circuit board. In addition to the carrying function, IC substrates also have additional functions such as protection circuits, dedicated lines, design of heat dissipation paths, and establishment of modular standards for components. High-end IC substrates (ABF substrates) are mainly used for packaging high-performance chips such as CPUs, GPUs, FPGAs, and ASICs, and are the cornerstone of big data and artificial intelligence.

[0003] IC substrates are stacked with materials of different thicknesses, and different signal layers are connected through tiny holes; substrate laser drilling refers to the use of laser technology to process tiny holes on the substrate.

[0004] At present, the aperture of micro-holes processed by laser drilling technology of substrates is between 70-150μm, and CO2 lasers and nanosecond ultraviolet lasers are mainly used for processing, which requires pre-treatment (brown oxidation, black oxidation, window opening, film lamination, surface copper thinning, etc.). With the outbreak of big data, artificial intelligence and the increasing requirements of IC substrates for advanced packaging technology, the number of IO points on the substrates is increasing and becoming more and more dense, which requires the aperture of micro-holes on the substrates to be further reduced. The aperture of laser drilling of the next generation of substrates will be between 10-100μm. The current mainstream laser drilling technology is complex to operate, the material is easy to delaminate, and the aperture of the drilled hole can no longer meet the needs of the next generation of substrates. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a laser drilling method and system capable of processing holes with a diameter of 10-100 μm, especially 20-70 μm.

[0006] In order to solve the above problems, the present invention proposes the following technical solutions:

[0007] In a first aspect, the present invention provides a laser drilling method, comprising using a pulse laser for drilling, and by adjusting the waveform of the pulse train emitted by the pulse laser and shaping the pulse train beam, a microhole with an aperture of 10-100 μm can be formed on the material to be processed; the pulse train output frequency of the pulse laser is 1-20 kHz, and the wavelength is 257-1064 nm; the pulse train includes at least two parts of sub-pulse waveforms, wherein, in order of precedence, the sub-pulse energy in the first part of the sub-pulse waveform is greater than the sub-pulse energy in the second part of the sub-pulse waveform.

[0008] Preferably, the pulse train comprises two sub-pulse waveforms, the sub-pulse energy in the first sub-pulse waveform is greater than or equal to 70% of the total energy of the pulse train, and the sub-pulse energy in the second sub-pulse waveform is less than 30% of the total energy of the pulse train.

[0009] Preferably, the pulse laser outputs a wavelength of 257-1064 nm, and a more preferred wavelength is 532 nm.

[0010] Preferably, the pulse laser is a femtosecond, picosecond or nanosecond laser.

[0011] Preferably, the pulse width of the pulse laser is less than 100 ns.

[0012] Preferably, the pulse width of the pulse laser is 2-20 ps.

[0013] Preferably, the pulses emitted by the pulse laser are output in the form of pulse trains.

[0014] Preferably, the number of pulses in the pulse train emitted by the pulse laser is greater than 50.

[0015] Preferably, the number of pulses in the pulse train emitted by the pulse laser is 50-300.

[0016] Preferably, the pulse train lasts longer than 10 μs. For example, the pulse train lasts for 20 μs, 50 μs, 80 μs, 100 μs, 150 μs, 200 μs, 300 μs, etc. Those skilled in the art can determine the pulse train duration according to the drilling plate and specification requirements.

[0017] In a second aspect, the present invention provides a laser drilling system for executing the laser drilling method described in the first aspect.

[0018] Preferably, the method comprises a pulse laser, a shaping system, a galvanometer system, a focusing system, a motion control system, a quality monitoring system, a software system and an auxiliary air blowing module. The Gaussian pulse emitted by the pulse laser is incident into the focusing system via the shaping system and the galvanometer system. The laser is emitted from the focusing system and is focused on the surface of the material to be processed. The shaping system is used for shaping the light beam. The motion control system controls the movement of the material to be processed on the processing plane. The auxiliary air blowing module is used for cooling and blowing the surface of the processed material. The quality monitoring system is used for monitoring the quality of drilling during the processing. The software system is used for process pretreatment and control of the drilling process.

[0019] Preferably, the laser drilling system further comprises a workbench, the material to be processed is arranged on the workbench, and the auxiliary blowing module is arranged on the workbench.

[0020] Furthermore, the laser drilling system also includes a 45° reflector, which is arranged between the shaping system and the focusing system and is used to convert the Gaussian pulse into a 90° direction and then inject it into the focusing system.

[0021] Furthermore, the shaping system includes a diffractive optical device to convert the Gaussian beam emitted by the pulsed laser into a flat-top beam or a quasi-flat-top beam. The diffractive optical device includes but is not limited to DOE (Diffractive Optical Elements), a phase plate, a pinhole aperture, a microlens array (Lens Array), and an aspheric lens.

[0022] Furthermore, the shaping system also includes a beam expander collimator and a galvanometer, and the focusing system is a field mirror; the Gaussian beam emitted by the pulsed laser passes through the diffraction optical device and the laser beam emitted by the beam expander collimator and is incident on the galvanometer in a horizontal direction, and is converted by 90° through the galvanometer and a 45° reflector and then vertically incident on the field mirror.

[0023] Compared with the prior art, the technical effects achieved by the present invention include:

[0024] The laser drilling method provided by the present invention adjusts the waveform of the pulse train emitted by the pulse laser and shapes the pulse train beam, and the output pulse train includes at least two parts of pulse waveforms. In order, the sub-pulse energy in the first part of the sub-pulse waveform is greater than the sub-pulse energy in the second part of the sub-pulse waveform. The present invention uses high-energy sub-pulses to quickly remove the surface material, and then outputs low-energy sub-pulses to avoid damaging the underlying material, so as to obtain micropores with an aperture of 10-100μm, especially micropores with an aperture of 20μm-70μm, which meet the technical requirements of IC carriers. The holes obtained by this laser method have no heat-affected zone, and the material is not easy to delaminate; there are no molten materials, craters, residual glue at the bottom of the hole, protruding glass fibers, etc. on the hole wall; the bottom of the hole is clean and has a hole washing effect; no pretreatment is required. The entire mechanism of action between the laser and the material is mainly cold processing removal, which greatly reduces the influence of thermal effects and ensures the taper and bottom smoothness of the drilled hole.

[0025] The laser drilling system provided by the present invention adjusts the waveform of the pulse train emitted by the pulse laser and shapes the pulse train beam through a shaping system to achieve the transformation of different beams, and can achieve drilling of holes with different apertures. The laser drilling system for drilling a carrier provided by the present invention only requires beam focusing and cooling and blowing steps, and does not require other pre-processing and post-processing work. The drilling process is simple and the drilling efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0027] Figure 1 A schematic diagram of a laser drilling system provided in an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of drilling a hole on a carrier board using a laser drilling method provided in an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a pulse train waveform of a laser drilling method provided by an embodiment of the present invention;

[0030] Figure 4 The figure is a processing effect diagram of the laser method executed by the laser drilling system for drilling holes in a carrier provided by an embodiment of the present invention.

[0031] Reference numerals

[0032] 1 software system, 2 quality monitoring system, 3 pulse laser, 4 shaping system, 5 projection mirror, 6 focusing system, 7 carrier board, 8 auxiliary blowing module, 9 workbench. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Similar component numbers in the drawings represent similar components. 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 creative work are within the scope of protection of the present invention.

[0034] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0035] It should also be understood that the terms used in this description of the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. As used in the description of the embodiments of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms.

[0036] Example 1

[0037] See also Figure 1 , an embodiment of the present invention provides a laser drilling system, which can be seen from the figure, including a software system 1, a quality monitoring system 2, a pulse laser 3, a shaping system 4, a transmitting mirror 5, a focusing system 6, a carrier plate 7, an auxiliary blowing module 8, and a workbench 9. Among them, the software system 1 is used to perform process pretreatment and control of the drilling process, the quality monitoring system 2 is used to monitor the quality of drilling during the processing, the Gaussian pulse emitted by the pulse laser 3 is incident into the focusing system 6 through the shaping system 4, and the pulse laser is emitted from the focusing system 6 and focused on the surface of the material to be processed. The material to be processed in this embodiment is the carrier plate 7, and the auxiliary blowing module 8 is used to cool and blow the surface of the processed material.

[0038] In a specific embodiment, a processing station is arranged on the workbench 9 . During processing, the carrier plate 7 is placed on the processing station, and the auxiliary blowing module 8 is arranged on the workbench 9 .

[0039] As can be seen from the figure, the shaping system 4 is used to shape the beam, and the shaping system 4 includes a diffractive optical device, which can convert the Gaussian beam emitted by the pulse laser 3 into a flat-top beam or a quasi-flat-top beam with sharp edges, clear edges and corners, and a taper close to 90 degrees, thereby ensuring the drilling effect. Suitable diffractive optical devices include but are not limited to DOE, phase plate, pinhole aperture, microlens array, aspherical lens, etc., which can improve the uniformity of the light spot and the drilling quality by adjusting the phase distribution and intensity distribution of the beam.

[0040] In a specific embodiment, the shaping system 4 further includes necessary optical lenses for expanding, shrinking and collimating the Gaussian pulses emitted by the pulse laser 3 .

[0041] In a specific embodiment, the laser drilling system further includes a reflector 5 , which is a 45° reflector. The 45° reflector is disposed between the shaping system 4 and the focusing system 6 , and is used to convert the direction of the laser beam by 90° and then incident on the focusing system 6 .

[0042] In a specific embodiment, the focusing system 6 is a field lens; the focusing system 6 focuses the flat-top beam onto the surface of the carrier 7 by imaging, removes the material, and drills a small hole that meets the aperture requirements.

[0043] The Gaussian pulse emitted by the pulse laser 3 passes through the diffraction optical device and the beam expander collimator, and then enters the galvanometer mirror in a horizontal direction. After being converted by 90° through the galvanometer mirror and the 45° reflector, the laser beam enters the field mirror vertically.

[0044] The laser drilling system provided in the embodiment of the present invention uses a shaping system to adjust the waveform of the pulse train emitted by the pulse laser and to shape the pulse train beam, thereby adjusting the intensity and phase of the laser beam, and can achieve drilling of different apertures. In combination with the laser method of drilling, the processing flow only requires beam focusing and cooling and blowing steps, and does not require other pre-processing and post-processing work. The drilling process is simple and the drilling efficiency is greatly improved.

[0045] Example 2

[0046] The embodiment of the present invention also provides a laser drilling method, which is applied to the laser drilling system for drilling holes in the carrier board of embodiment 1. The laser method includes using a pulse laser for drilling holes, and by adjusting the waveform of the pulse train emitted by the pulse laser and shaping the pulse train beam, a micro-hole with an aperture less than or equal to 100 μm, especially an aperture of 20 μm-70 μm, can be formed on the carrier board to be processed; the pulse train output frequency of the pulse laser is 1-20 kHz, and the wavelength is 257-1064 nm; the pulse train includes at least two parts of sub-pulse waveforms, wherein, in order of precedence, the sub-pulse energy in the first part of the sub-pulse waveform is greater than the sub-pulse energy in the second part of the sub-pulse waveform.

[0047] In a specific embodiment, the pulse train includes two seed pulse waveforms, the sub-pulse energy in the first sub-pulse waveform is greater than or equal to 70% of the total energy of the pulse train, and the sub-pulse energy in the second sub-pulse waveform is less than 30% of the total energy of the pulse train.

[0048] In a specific embodiment, the pulse laser is a femtosecond, picosecond or nanosecond laser.

[0049] In a specific embodiment, the pulse width of the pulse laser is less than 100 ns, preferably 2-20 ps, ​​and more preferably 5-15 ps.

[0050] In a specific embodiment, the pulses of the pulse laser are output in the form of pulse trains.

[0051] In a specific embodiment, the number of pulses in the pulse train emitted by the pulse laser is greater than 50, preferably 50-300.

[0052] In a specific embodiment, the pulse train lasts for more than 10 μs, such as between 30-100 μs.

[0053] For example, in one embodiment, see Figure 2 , which is a schematic diagram of drilling a carrier board using the system of Example 1 and the method of Example 2. When performing laser drilling, the electronic material on the carrier board is mainly drilled, and it is required to remove the electronic material without damaging the copper clad board, while ensuring the taper of the electronic material drilling.

[0054] In this embodiment, the pulse width of the pulse laser is 10ps, the wavelength is 532nm, the frequency of the pulse laser is 5KHz, the number of pulses in the pulse train is 300, and the energy of a single pulse train is 7mj. Figure 3 In order to ensure the drilling effect and improve the material removal efficiency, the waveform of the pulse train is adjusted in this embodiment, as shown in the schematic diagram. Figure 3 As shown, according to the processing time sequence, the pulse energy of the front sub-pulse is controlled to increase. In this embodiment, the sub-pulse energy is 12μj, and the duration is 60μs, which can increase the material removal rate; then the subsequent sub-pulse is controlled to reduce the pulse energy. In this embodiment, the sub-pulse energy is 6μj, and the duration is 40μs, which can prevent damage to the underlying copper plate.

[0055] The pulse laser of this embodiment can accurately control the power of the laser through the acousto-optic device, and the pulse waveform can be accurately adjusted through software. By adjusting the pulse energy and waveform, the laser power density can be greater than the damage threshold of the material without damaging the copper substrate at the bottom, and the substrate with a 50μm aperture and a 40μm thickness can be drilled.

[0056] The effect of the carrier plate obtained by drilling according to the above processing parameters is shown in Figure 4 ,Depend on Figure 4 It can be seen that the holes obtained by laser drilling on the carrier board in the embodiment of the present invention have good taper and a hole diameter between 20-70 μm, the copper clad board is intact, and the removal effect of the electronic material is good.

[0057] Further referring to Table 1 below, a specific example is provided in which the system of Example 1 and the method of Example 2 are used to drill holes in a carrier plate by controlling laser parameters to obtain microholes less than or equal to 100 μm.

[0058] Table 1 Laser parameters of different holes

[0059]

[0060] It can be seen from the results in Table 1 that, under the conditions of certain pulse width, wavelength and frequency, by adjusting the waveform of the pulse train emitted by the pulse laser and shaping the pulse train beam, the output pulse train is adjusted to include at least two parts of sub-pulse waveforms, and the sub-pulse energy in the first part of the sub-pulse waveform and the sub-pulse energy in the second part of the sub-pulse waveform are adjusted, high-quality micropores with an aperture of 10-100μm, especially an aperture of 20μm-70μm, can be obtained.

[0061] It is understandable that in other embodiments, the thicker the electronic material on the carrier board is, the greater the energy and the longer the time required for laser drilling to effectively ensure sufficient removal of the material and the taper of the drilled hole.

[0062] The laser drilling method provided in the embodiment of the present invention uses ultrafast pulses and adjustable pulse waveforms and beam shaping, and uses more sub-pulses to achieve material removal, thereby obtaining microholes with an aperture of 10-100μm, especially with an aperture of 20μm-70μm. The laser drilling method has the advantages of no heat-affected zone, and the material is not easy to delaminate; there are no molten materials, craters, residual glue at the bottom of the hole, protruding glass fibers, etc. on the hole wall; the bottom of the hole is clean and has a hole washing effect; no pretreatment is required, etc. The entire mechanism of action of the laser and the material is mainly cold processing removal, which greatly reduces the impact of thermal effects and ensures the taper and bottom smoothness of the drilled hole.

[0063] The laser drilling method provided in the embodiment of the present invention can be used for the production of circuit boards. The carrier board can be directly laser drilled during the drilling process without the need for film pasting and window opening. By adding a diffraction optical device to the laser drilling system, the laser waveform can be adjusted according to the conditions of the processing material during the laser processing, thereby improving the material removal efficiency and drilling efficiency.

[0064] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0065] The above is a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A laser drilling method, characterized in that: A pulse laser is used for drilling; by adjusting the waveform of the pulse train emitted by the pulse laser and shaping the pulse train beam, a microhole with an aperture of 10-100 μm can be formed on the material to be processed; the pulse train includes at least two parts of sub-pulse waveforms, wherein, in order of sequence, the sub-pulse energy in the first part of the sub-pulse waveform is greater than the sub-pulse energy in the second part of the sub-pulse waveform.

2. The laser drilling method according to claim 1, characterized in that: The pulse train output frequency of the pulse laser is 1-20kHz, and the wavelength is 257-1064nm.

3. The laser drilling method according to claim 1, characterized in that: The pulse train comprises two parts of sub-pulse waveforms, the sub-pulse energy in the first part of the sub-pulse waveform is greater than or equal to 70% of the total energy of the pulse train, and the sub-pulse energy in the second part of the sub-pulse waveform is less than 30% of the total energy of the pulse train.

4. The laser drilling method according to claim 1, characterized in that: The pulse laser is a femtosecond, picosecond or nanosecond laser.

5. The laser drilling method according to claim 1, characterized in that: The pulse width of the pulse laser is less than 100 ns.

6. The laser drilling method according to claim 1, characterized in that: The number of pulses in the pulse train emitted by the pulse laser is greater than 50.

7. The laser drilling method according to claim 6, characterized in that: The pulse train lasts for more than 10 μs.

8. A laser drilling system, characterized in that: Used to perform the laser drilling method described in any one of claims 1-7.

9. The laser drilling system according to claim 8, characterized in that: It includes a pulse laser, a shaping system, a galvanometer system, a focusing system, a motion control system, a quality monitoring system, a software system and an auxiliary blowing module. The Gaussian pulse emitted by the pulse laser is incident into the focusing system via the shaping system and the galvanometer system. The laser is emitted from the focusing system and focused on the surface of the material to be processed. The shaping system is used for shaping the light beam. The motion control system controls the movement of the material to be processed on the processing plane. The auxiliary blowing module is used for cooling and blowing the surface of the processed material. The quality monitoring system is used for monitoring the quality of drilling during the processing. The software system is used for process pretreatment and control of the drilling process.

10. The laser drilling system according to claim 9, characterized in that: The shaping system includes a diffractive optical device to convert a Gaussian beam emitted by a pulsed laser into a flat-top beam or a quasi-flat-top beam. The diffractive optical device includes but is not limited to a DOE, a phase plate, a pinhole aperture, a microlens array, and an aspheric lens.

Images