Dual-beam common-cavity solid laser based on mobile pumping module and PCB processing method

Abstract

The application provides a double-beam common-cavity solid laser based on a mobile pumping module and a PCB processing method, the double-beam common-cavity solid laser comprising a first pumping module, a first laser crystal, a second pumping module, a second laser crystal, an infrared full-reflection mirror, an infrared turning mirror and an infrared output mirror; further comprising a first driving assembly for driving the first pumping module to move along a direction perpendicular to an axis of the first laser crystal, by adjusting the position of the first pumping module, the center position of the thermal lens in the first laser crystal is changed, thereby adjusting the included angle or parallel spacing between the two output laser beams. The application utilizes a single resonant cavity to output two independent laser beams, realizes double-beam sharing of the resonant cavity, a cooling system and a power supply system, and compared with a traditional double-head scheme, the cost is significantly reduced, meanwhile, without an external complex optical path, the spacing between the two laser focal points can be adjusted at any time only by moving the position of the first pumping module, thereby avoiding the optical path alignment problem caused by external mechanical adjustment of the lens.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, specifically relating to a dual-beam common-cavity solid-state laser based on a mobile pump module and a PCB processing method. Background Technology

[0002] In modern microelectronics manufacturing, especially in the production of printed circuit boards (PCBs) and flexible printed circuit boards (FPCs), "high throughput" and "high precision" are always contradictory demands that coexist. As consumer electronics devices become thinner and more integrated, the component density on PCBs is increasing exponentially. This not only requires laser processing equipment to have micron-level positioning accuracy but also poses extremely high challenges to processing speed. Traditional single-beam laser processing systems, whether using nanosecond ultraviolet lasers or ultrafast picosecond / femtosecond lasers, are limited in processing efficiency by the matching relationship between the galvanometer scanning speed (typically on the order of several meters per second) and the laser repetition rate.

[0003] To overcome the physical limitations of single-point machining, "parallel machining" has become an industry consensus. Current parallel machining solutions are mainly divided into two categories: one is a physical "dual-head" system, which involves installing two completely independent lasers and beam systems on a gantry; the other is to use diffractive optical elements (DOE) or beam splitters to split a single laser beam into two beams in an external beam.

[0004] However, both of these solutions have significant drawbacks in practical applications:

[0005] (1) Cost redundancy of physical dual-head system: Installing two lasers not only takes up a lot of space, but also means double the cost of light source, double the cooling load and double the maintenance cost. For the PCB manufacturing industry with increasingly squeezed profit margins, this linearly increasing cost structure is unacceptable.

[0006] (2) Lack of flexibility of external fixed beam splitting: Although traditional DOE or prism beam splitting schemes reduce the cost of light sources, their beam splitting angle and focal spot spacing are fixed, or they require extremely complex external mechanical displacement stages to adjust the reflector group to change the spacing. In PCB panel processing, due to the thermal expansion and contraction of materials or batch tolerances, the actual spacing between panel units often changes slightly. This fixed dual-beam system cannot adapt to such changes, resulting in a decrease in processing accuracy or forced frequent replacement of optical components, which seriously affects production efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a dual-beam co-cavity solid-state laser based on a mobile pump module, which can at least solve some of the defects existing in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A dual-beam co-cavity solid-state laser based on a mobile pump module includes a first pump module, a first laser crystal, a second pump module, a second laser crystal, and an infrared output mirror. The first pump module pumps the first laser crystal to form a first laser beam, and the second pump module pumps the second laser crystal to form a second laser beam. An infrared total reflection mirror is disposed between the first pump module and the first laser crystal to totally reflect the light incident from the first laser crystal. An infrared deflector is disposed between the first laser crystal and the second laser crystal to fold the first laser beam and the second laser beam into the same resonant cavity. The infrared output mirror is disposed at the end of the second laser crystal away from the infrared deflector to output the first laser beam and the second laser beam. The laser also includes a first driving component for driving the first pump module to move in a direction perpendicular to the axis of the first laser crystal.

[0010] Furthermore, the first laser crystal and the second laser crystal are arranged at a 90° angle to each other.

[0011] Furthermore, the effective light transmission cross-sectional area of ​​the first laser crystal is larger than that of the second laser crystal.

[0012] Furthermore, the infrared deflector is a hyperbolic ring mirror or a hyperbolic cylindrical mirror, the radius of curvature of which is configured to compensate for resonant cavity astigmatism caused by nonnormal incidence.

[0013] Furthermore, the displacement of the first pump module satisfies the following relationship: Where ΔY is the change in the distance between the focal points of the two laser beams on the focal plane; F obj θ is the focal length of the F-theta field mirror through which the laser output passes; out M represents the optical axis angular offset at the laser output end. exp S is the magnification of the beam expander; S is the sensitivity factor; Δx p f represents the displacement of the first pump module. th The focal length is the internal thermal lens of the first laser crystal.

[0014] Furthermore, the aforementioned dual-beam common-cavity solid-state laser also includes a compensation adjustment component for detuning the first laser beam and the second laser beam.

[0015] Furthermore, the compensation adjustment component includes a second driving component for driving the deflection angle of the infrared total reflection mirror, and a second acousto-optic modulator for correcting the optical axis of the first laser beam; the second acousto-optic modulator is disposed between the second laser crystal and the infrared output mirror.

[0016] Furthermore, the compensation adjustment component also includes a first acousto-optic modulator for correcting the optical axis of the second laser beam, the first acousto-optic modulator being disposed between the second laser crystal and the infrared output mirror.

[0017] Furthermore, the output end of the infrared output mirror is provided with a quarter infrared glass plate.

[0018] In addition, the present invention also provides a PCB processing method using the above-mentioned dual-beam common-cavity solid-state laser, comprising the following processes:

[0019] S1. Measure the actual unit spacing of the PCB panel to be processed, and calculate the difference between the actual unit spacing and the focal distance between the current first laser beam and the second laser beam of the dual-beam co-cavity solid-state laser.

[0020] S2. Move the first pump module until the focal distance between the first laser beam and the second laser beam matches the actual unit spacing of the PCB panel to be processed.

[0021] S3. Turn on the laser output and use the first laser beam and the second laser beam to perform laser processing on the two units of the PCB panel respectively.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The dual-beam co-cavity solid-state laser provided by the present invention uses a single resonant cavity to output two independent laser beams, realizing the dual beams sharing the resonant cavity, cooling system and power supply system. Compared with the traditional dual-head laser solution, the cost is significantly reduced. At the same time, there is no need for external complex optical path. The micron-level dual beam focal distance can be corrected by simply moving the position of the first pump module. It perfectly adapts to the expansion and contraction compensation of the PCB board, avoids the optical path alignment problem caused by external mechanical adjustment of the lens, and utilizes the adaptive mode characteristics in the resonant cavity to achieve higher beam pointing stability, ensuring stable power and reliable processing accuracy during the processing.

[0024] (2) The dual-beam co-cavity solid-state laser provided by the present invention achieves detuning compensation for the first laser beam and the second laser beam by designing a "mechanical-electronic" hybrid compensation mechanism, which solves the physical problem that traditional orthogonal AOM cannot simultaneously perform optical axis correction in a single direction, and improves the stability of laser power.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the dual-beam concavity solid-state laser of the present invention;

[0027] Figure 2This is a schematic diagram of resonance control and compensation in this invention; wherein, the red line is the optical path of the stimulated emission light of the first laser crystal; and the blue dashed line is the optical path of the stimulated emission light of the second laser crystal.

[0028] Explanation of reference numerals in the attached figures: 1. First pump module; 2. Infrared total reflection mirror; 3. First laser crystal; 4. Second pump module; 5. Infrared deflection mirror; 6. Second laser crystal; 7. First acousto-optic modulator; 8. Second acousto-optic modulator; 9. Infrared output mirror; 10. Quarter infrared glass slide. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection", and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an abutting connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] like Figure 1 and Figure 2As shown, this embodiment provides a dual-beam common-cavity solid-state laser based on a moving pump module, including a first pump module 1, a first laser crystal 3, a second pump module 4, a second laser crystal 6, an infrared total reflection mirror 2, an infrared deflector 5, and an infrared output mirror 9. These optical components are arranged in a certain optical path order to form a V-shaped or Z-shaped folded resonant cavity. The infrared total reflection mirror 2 is disposed between the first pump module 1 and the first laser crystal 3, and can transmit pump light while reflecting infrared laser light. The infrared deflector 5 is disposed between the first laser crystal 3 and the second laser crystal 6, and can transmit pump light while reflecting infrared laser light. The infrared output mirror 9 is disposed at the end of the second laser crystal 6 away from the infrared deflector 5. It also includes a first driving component (not shown in the figure) for driving the first pump module 1 to move in a direction perpendicular to the axis of the first laser crystal 3.

[0034] Specifically, such as Figure 2 As shown, the first pump module 1 pumps the first laser crystal 3, forming a first thermal lens channel within the first laser crystal 3. The first laser crystal 3 radiates photons, forming a first laser beam (i.e., Figure 2 (Middle red line) The first laser beam is emitted from one end of the first laser crystal 3, totally reflected back to the first laser crystal 3 by the infrared total reflection mirror 2, and after being amplified by the first laser crystal 3, it is output from the other end of the first laser crystal 3; at the same time, the second pump module 4 pumps the second laser crystal 6, forming a second thermal lens channel within the second laser crystal 6, and the second laser crystal 6 radiates photons to form the second laser beam (i.e., Figure 2 (Middle blue dashed line) The second laser beam is emitted from one end of the second laser crystal 6, reflected by the infrared deflector 5, passes through the first laser crystal 3, is totally reflected back by the infrared total reflection mirror 2, passes through the first laser crystal 3 again, is reflected back to the second laser crystal 6 by the infrared deflector 5, and after being amplified by the second laser crystal 6, is output from the other end of the second laser crystal 6 and directed towards the infrared output mirror 9; during this process, the infrared deflector 5 folds the first laser beam and the second laser beam into the same resonant cavity, that is, both the first laser beam and the second laser beam are constrained within the resonant cavity formed by the infrared total reflection mirror 2 and the infrared output mirror 9; after being refracted by the infrared deflector 5, the first laser beam passes through the second laser crystal 6 and is directed towards the infrared output mirror 9, and both the first laser beam and the second laser beam are output through the infrared output mirror 9. When it is necessary to adjust the distance between the two output laser beams on the processing plane, the first driving component is controlled to drive the first pump module 1 to move. Due to the thermal lens effect, the position of the center of the thermal lens in the first laser crystal 3 will change with the movement of the pump spot of the first pump module 1, thereby adjusting the angle or parallel distance between the output first laser beam and the second laser beam, realizing that the focal distance between the two laser beams can be adjusted at any time.

[0035] Preferably, the first laser crystal 3 and the second laser crystal 6 are designed with special crystal axis tangents or relative angles. Specifically, the first laser crystal 3 and the second laser crystal 6 are arranged at 90° relative to each other. This design allows the first laser beam and the second laser beam to have orthogonal polarization states, thereby suppressing gain competition between the two optical paths.

[0036] To accommodate the lateral movement requirements of the first pump module 1 and provide sufficient optical redundancy for thermal lens center offset and dynamic optical axis adjustment, the effective light-transmitting cross-section size of the first laser crystal 3 is optimized to be larger than that of the second laser crystal 6. Simultaneously, the two laser beams share the same resonant cavity and have orthogonal polarization states (S-beam and P-beam). The difference in the effective light-transmitting cross-section size between the first laser crystal 3 and the second laser crystal 6 further enhances mode isolation and avoids mutual interference. The effective light-transmitting cross-section size refers to the cross-sectional parameter of the effective region in the laser crystal that can participate in laser oscillation. For a slab-shaped crystal, the effective light-transmitting cross-section size is width × thickness; for a rod-shaped crystal, the effective light-transmitting cross-section size is diameter.

[0037] In this invention, since the infrared deflector 5 functions to fold the two optical paths of the first laser crystal 3 and the second laser crystal 6 into the same resonant cavity (V-type or Z-type folded cavity), the angle at which the beam is incident on the infrared deflector 5 is not 90° normal incidence, but rather a tilted incident angle θ (non-normal incidence). This non-normal incidence directly induces resonant cavity astigmatism, which exacerbates mode competition between the two optical paths (the two beams of orthogonally polarized light are affected by astigmatism to different degrees), leading to output power fluctuations, decreased beam stability, and disruption of resonant cavity mode matching, resulting in reduced laser oscillation efficiency and failure to fully utilize the power potential of the dual gain units (i.e., the first laser crystal and the second laser crystal). Therefore, to compensate for the resonant cavity astigmatism caused by non-normal incidence, this embodiment optimizes the design of the infrared deflector 5 by using a double-curvature ring mirror or a double-curvature cylindrical mirror, whose radius of curvature is configured to compensate for the resonant cavity astigmatism caused by non-normal incidence. Specifically, the double radius of curvature of the infrared deflector 5 must satisfy the following relationship: , where R T and R S θ represents the radii of curvature in the two directions (meridian plane and sagittal plane) of the infrared deflector 5, respectively, and θ is the actual incident angle of the light beam onto the infrared deflector 5.

[0038] In some embodiments, the first driving component may be, but is not limited to, a linear displacement slide; the mapping relationship between the displacement of the first pump module 1 driven by the first driving component and the distance between the focal points of the two laser beams (i.e., the first laser beam and the second laser beam) on the focal plane is as follows:

[0039] ;

[0040] Where △Y represents the change in the distance between the focal points of the two laser beams on the focal plane (i.e., the final PCB panel fitting distance that needs to be adjusted); F obj θ is the focal length of the F-theta field mirror through which the laser output passes; out M represents the optical axis angle shift at the laser output end (i.e., the change in the optical axis angle of the first laser beam caused by the movement of the first pump module, in radians); exp S is the magnification of the beam expander; S is the sensitivity factor; Δx p f represents the displacement of the first pump module. th Let be the focal length of the thermal lens within the first laser crystal (determined by the pump power). Using this formula, the displacement Δx of the first pump module can be calculated in reverse, based on the final required adjustment of the PCB panel adapter spacing. p Therefore, without the need for complex external optical paths, micron-level focal distance correction can be achieved simply by moving the first pump module, perfectly adapting to the expansion and contraction compensation of PCB panels.

[0041] Moreover, it can be seen from the above formula that in order to expand the adjustment range of ΔY to accommodate more PCB panel spacing, it can be achieved in the following ways: (1) Reduce the beam expansion ratio M exp (2) Select crystals with stronger thermal lensing effect to reduce f th Value, such as Replace Nd:YAG; (3) Optimize the resonant cavity structure, such as appropriately increasing the cavity length to increase the sensitivity factor S.

[0042] In the optimized implementation, after moving the position of the first pump module 1, the first laser beam and the second laser beam will become eccentric due to the crystal thermal lens effect, which causes them to deviate from the optical axis. This will eventually lead to unstable or reduced laser power. To address this, the dual-beam co-cavity solid-state laser in this embodiment also includes a compensation adjustment component for detuning the first laser beam and the second laser beam.

[0043] In one specific embodiment, the compensation adjustment component includes a second driving component (not shown in the figure) for driving the deflection angle of the infrared total reflection mirror 2, and a second acousto-optic modulator 8 for correcting the optical axis of the first laser beam; the second acousto-optic modulator 8 is disposed between the second laser crystal 6 and the infrared output mirror 9. In this embodiment, for the second laser beam whose polarization state is perpendicular to the thermal lens displacement direction (i.e., S-polarized beam), its optical axis correction is achieved by the active deflection of the infrared total reflection mirror 2 driven by the second driving component. In some embodiments, the second driving component can be a rotatable platform or an adjustable frame structure. For the first laser beam whose polarization state is parallel to the thermal lens displacement direction (i.e., P-polarized beam), its optical axis correction is achieved by adjusting the Bragg diffraction angle shift generated by the radio frequency driving frequency of the corresponding second acousto-optic modulator 8. Through this "mechanical-electronic" hybrid compensation mechanism design, that is, the S-beam is corrected by "infrared total reflection mirror mechanical deflection" and the P-beam is corrected by "acousto-optic modulator (AOM) radio frequency frequency adjustment", the two correction schemes are controlled independently, respectively targeting the polarization characteristics and drift laws of the two beams, to achieve detuning compensation for the first and second laser beams, ensuring that the two beams can maintain stable optical axis transmission during the focal distance adjustment process, avoiding mutual interference, solving the physical problem that traditional orthogonal AOMs cannot simultaneously perform optical axis correction in a single direction, and improving the stability of laser power.

[0044] Furthermore, the compensation and adjustment component also includes a first acousto-optic modulator 7 for correcting the optical axis of the second laser beam. The first acousto-optic modulator 7 is disposed between the second laser crystal 6 and the infrared output mirror 9. Through the synergistic effect of the mechanical deflection of the infrared total reflection mirror 2 and the radio frequency parameter adjustment of the first acousto-optic modulator 7 corresponding to the polarization (S-polarization) of the second laser beam, dynamic compensation for the drift of the second laser beam is achieved, ensuring that the second laser beam always transmits along the design reference in the resonant cavity, avoiding interference or mode competition with the first laser beam (corresponding to P-polarization), and ultimately ensuring the pointing stability, power stability and mode consistency of the dual-beam output. Specifically, the synergistic effect of the mechanical deflection of the infrared total reflection mirror 2 and the radio frequency parameter adjustment of the first acousto-optic modulator 7 is as follows: the active deflection of the infrared total reflection mirror 2 performs coarse adjustment on the optical axis angle drift caused by the thermal lens offset, and quickly cancels most of the angle deviation through the geometric optical reflection law to ensure that the beam propagates roughly along the designed optical path; the radio frequency parameter adjustment of the first acousto-optic modulator 7 performs fine adjustment on the small optical axis offset (including angle deviation and lateral translation) remaining after the coarse adjustment of the infrared total reflection mirror 2, and uses the angle sensitivity of Bragg diffraction to compensate for the minor error, while suppressing the mode detuning caused by the optical path drift.

[0045] In an optimized configuration, the output end of the infrared output mirror 9 is provided with a quarter-infrared glass plate 10, so that both mutually orthogonally polarized beams are converted into circularly polarized light, thereby reducing the difference in the properties of the material caused by the different polarization.

[0046] The PCB fabrication process using the dual-beam common-cavity solid-state laser of this embodiment is as follows:

[0047] S1. Use a vision system to identify the actual unit spacing of the PCB panel to be processed, and calculate the difference between the actual unit spacing and the focal distance between the current first laser beam and the second laser beam of the dual-beam co-cavity solid-state laser; this difference is the final PCB panel adaptation spacing that needs to be adjusted, and the displacement that the first pump module 1 needs to move can be calculated from this.

[0048] S2. Based on the displacement of the first pump module 1 calculated in step S1, move the first pump module 1 until the focal distance between the first laser beam and the second laser beam matches the actual unit distance of the PCB panel to be processed.

[0049] S3. The deflection angle of the infrared total reflection mirror 2 and the radio frequency power of the first acousto-optic modulator 7 and the second acousto-optic modulator 8 are adjusted by power feedback PID to compensate for the detuning of the first laser beam and the second laser beam.

[0050] S4. Turn on the laser output and use the first laser beam and the second laser beam to perform laser processing (such as marking or cutting) on ​​the two units of the PCB panel respectively.

[0051] In this embodiment, the precise adjustment of the focal distance between the two beams is achieved by moving the first pump module, which adapts to the spacing changes of the PCB panel. During the processing, the beam direction is stable, the power is stable, and the processing accuracy is high, effectively improving the processing efficiency and processing quality.

[0052] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A dual-beam concavity solid-state laser based on a mobile pump module, characterized in that, The system includes a first pump module, a first laser crystal, a second pump module, a second laser crystal, and an infrared output mirror. The first pump module pumps the first laser crystal to form a first laser beam, and the second pump module pumps the second laser crystal to form a second laser beam. An infrared total reflection mirror is disposed between the first pump module and the first laser crystal to completely reflect the light incident from the first laser crystal. An infrared deflector is disposed between the first laser crystal and the second laser crystal to fold the first laser beam and the second laser beam into the same resonant cavity. The infrared output mirror is disposed at the end of the second laser crystal away from the infrared deflector to output the first laser beam and the second laser beam. The system also includes a first driving component for driving the first pump module to move in a direction perpendicular to the axis of the first laser crystal. The displacement of the first pump module satisfies the following relationship: Where ΔY is the change in the distance between the focal points of the two laser beams on the focal plane; F obj θ is the focal length of the F-theta field mirror through which the laser output passes; out M represents the optical axis angular offset at the laser output end. exp S is the magnification of the beam expander; S is the sensitivity factor; Δx p f represents the displacement of the first pump module. th The focal length is the internal thermal lens of the first laser crystal.

2. The dual-beam concavity solid-state laser as described in claim 1, characterized in that, The first laser crystal and the second laser crystal are arranged at a 90° angle relative to each other.

3. The dual-beam concavity solid-state laser as described in claim 1, characterized in that, The effective light transmission cross-sectional area of ​​the first laser crystal is larger than that of the second laser crystal.

4. The dual-beam concavity solid-state laser as described in claim 1, characterized in that, The infrared deflector is a hyperbolic ring mirror or a hyperbolic cylindrical mirror, and its radius of curvature is configured to compensate for resonant cavity astigmatism caused by nonnormal incidence.

5. The dual-beam concavity solid-state laser as described in claim 1, characterized in that, It also includes a compensation adjustment component for detuning the first laser beam and the second laser beam.

6. The dual-beam concavity solid-state laser as described in claim 5, characterized in that, The compensation and adjustment assembly includes a second driving assembly for driving the deflection angle of the infrared total reflection mirror, and a second acousto-optic modulator for correcting the optical axis of the first laser beam; the second acousto-optic modulator is disposed between the second laser crystal and the infrared output mirror.

7. The dual-beam concavity solid-state laser as described in claim 6, characterized in that, The compensation and adjustment assembly further includes a first acousto-optic modulator for correcting the optical axis of the second laser beam, the first acousto-optic modulator being disposed between the second laser crystal and the infrared output mirror.

8. The dual-beam concavity solid-state laser as described in claim 1, characterized in that, The output end of the infrared output mirror is equipped with a quarter infrared glass plate.

9. A PCB manufacturing method, characterized in that, The dual-beam concavity solid-state laser according to any one of claims 1-8 comprises the following process: S1. Measure the actual unit spacing of the PCB panel to be processed, and calculate the difference between the actual unit spacing and the focal distance between the current first laser beam and the second laser beam of the dual-beam co-cavity solid-state laser. S2. Move the first pump module until the focal distance between the first laser beam and the second laser beam matches the actual unit spacing of the PCB panel to be processed. S3. Turn on the laser output and use the first laser beam and the second laser beam to perform laser processing on the two units of the PCB panel respectively.

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