Laser processing system for improving efficiency of PCB blind hole based on AOD polarization

Abstract

The utility model provides a kind of laser processing system based on AOD polarized light promotes PCB blind hole efficiency, including laser and optical path device, the laser export place is provided with variable magnification beam expander, one-dimensional AOD is equipped behind variable magnification beam expander, and the two beams of light after one-dimensional AOD are sequentially processed to material to reach the purpose of blind hole one-time forming, without doing second time jump, the output time and output energy of two beams of light can be controlled in real time by computer, this method can be regulated focus position in real time using a laser, save mechanical moving time, improve optical path stability simultaneously.

Description

Technical Field

[0001] This utility model relates to the field of laser processing, and in particular to a laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization. Background Technology

[0002] Acousto-optic deflectors, or AODs for short, are devices made based on the principle of deflection. They can change the angle of a laser beam through an interaction mechanism.

[0003] Laser micro-hole drilling technology has been widely used in many fields such as aerospace, automotive manufacturing, machinery, and automatic control. Compared with traditional micro-hole drilling, laser micro-hole drilling technology has advantages such as smooth and flat cut surfaces, high precision, and high efficiency. It is especially suitable for high-precision devices such as semiconductor integrated chips and through-hole and blind-hole drilling of multi-layer PCBs, which is unmatched by traditional processing technologies. Since its emergence in the 1950s, PCB has been continuously developing towards miniaturization and integration. In recent years, the continuous development of the 3C industry (the information and home appliance industry integrating three major technology products) has further increased the demand and difficulty of PCB boards. Therefore, the requirements for the quality and efficiency of PCB laser drilling are becoming increasingly higher.

[0004] Currently, the most common PCB drilling methods are mechanical drilling and laser processing. Mechanical drilling is limited by the size of the drill bit, making it difficult to process holes smaller than 0.1mm. It also has high maintenance costs and low processing efficiency. Compared to mechanical drilling, laser drilling can achieve smaller hole diameters, and it is more efficient and less expensive, making it increasingly popular in the market. Laser drilling processes mainly include through-holes and blind holes. Taking double-sided boards as an example, through-holes utilize the high energy density of a focused laser to directly drill through the double-sided board, forming a circular through-hole. Blind holes, on the other hand, remove the surface copper and dielectric layer, without penetrating the underlying copper. Because the absorption coefficients of copper and the dielectric layer to lasers differ greatly, and because there must be no residual dielectric or molten copper in the underlying copper during processing, the blind hole process requires two steps. The first step is to remove the surface copper to expose the dielectric layer; the second step is to adjust the focal height and laser energy to clean the dielectric layer. Currently, there are two main technologies for blind hole processing: single-laser processing, where the surface copper is processed first, and then the dielectric layer is processed by adjusting the z-axis height and laser energy; and dual-laser processing, where the first laser processes the surface copper, and the second laser processes the dielectric layer. In this case, the second laser is already in defocus mode, so there is no need to change the z-axis height. Dual-laser blind hole processing can save the mechanical z-axis lifting time and form the hole in one pass, greatly improving the processing efficiency. However, spatial beam combining of the two laser beams is difficult, and the stability is poor due to mechanical vibration and stress of the equipment. Therefore, it is urgent to develop a more efficient and stable blind hole processing technology. Utility Model Content

[0005] To address the problems in existing technologies, this utility model provides a laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization. The system includes a laser and optical path components. A variable-magnification beam expander is located at the laser's exit point, and a one-dimensional AOD is positioned behind it. The beam passing through the one-dimensional AOD passes through a first pinhole aperture to a beam splitter, then is reflected by a third mirror and enters a galvanometer and telecentric field mirror, where it is focused onto a focal plane for the windowing process. The beam then passes through the one-dimensional AOD again, which deflects it, causing it to propagate along another optical path. This allows the beam to first pass through a first mirror in the other optical path, then through a second pinhole aperture, then through a concave lens to change its divergence angle, and then be reflected by a second mirror to reach the beam splitter. After being reflected by a third mirror, it enters the galvanometer and telecentric field mirror, ultimately focusing on the processed product for the adhesive removal process to achieve micro-via processing.

[0006] As a further improvement of this utility model, the first and second pinhole apertures are perpendicular to the light beam, and the aperture diameter can be adjusted.

[0007] As a further improvement of this utility model, the central axis of the light-transmitting aperture of the one-dimensional AOD coincides with the optical path.

[0008] As a further improvement of this utility model, the second and third reflecting mirrors are at 45° to the incident beam and the reflected beam, respectively.

[0009] As a further improvement of this utility model, the incident aperture of the galvanometer is perpendicular to the incident beam, and the exit aperture is perpendicular to the exit beam.

[0010] As a further improvement of this utility model, the telecentric field mirror and the galvanometer exit hole are connected by threads.

[0011] The beneficial effects of this utility model are:

[0012] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a laser processing system for improving the efficiency of blind vias in PCBs based on AOD (Acoustic Oscillator) polarization. When the incident light interacts with the acoustic grating, beam deflection occurs based on the Bragg diffraction effect, and the deflection angle is precisely controlled by the acoustic frequency. The beam path can be dynamically adjusted by changing the acoustic frequency in real time, and the response time of this process can reach the microsecond level. In actual blind via laser processing, the standard processing method generally adopts a "windowing first, then adhesive removal" timing control, with windowing as stage T1 and adhesive removal as stage T2. By setting the corresponding frequency parameters in stages T1 and T2 respectively through the AOD acousto-optic deflection system, the beam path can be precisely switched during the processing. One beam does not undergo beam shaping for the windowing process, while the other beam uses a lens to change the divergence angle to move the focal position before performing the adhesive removal process.

[0013] In summary, by processing the material sequentially with two beams of light, a blind hole can be formed in one step without the need for a second jump. The output time and energy of the two beams can be controlled in real time by a computer. This method can use a single laser to adjust the focal position in real time, saving mechanical movement time and improving the stability of the optical path. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization.

[0015] Figure 2 This is a schematic diagram illustrating the working principle of the AOD (Audio-Optical Deflector).

[0016] The names of the components in the diagram are as follows:

[0017] 1. Laser; 2. Variable magnification beam expander; 3. One-dimensional AOD; 4. First reflecting mirror; 5. Second pinhole aperture; 6. Concave lens; 7. Second reflecting mirror; 8. First pinhole aperture; 9. Beam splitter; 10. Third reflecting mirror; 11. Galvanometer; 12. Telecentric field mirror; 13. Focused beam; 14. Defocused beam; 15. Focused plane; 16. Defocused plane; 21. AOD acousto-optic deflector frame; 22. Acousto-optic crystal. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] A laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization is a system that uses acousto-optic defocusing to achieve defocusing.

[0020] A laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization includes a laser 1 and optical path devices. A variable magnification beam expander 2 is provided at the exit of the laser 1. A one-dimensional AOD 3 is provided behind the variable magnification beam expander 2. The beam passing through the one-dimensional AOD 3 first passes through the first pinhole aperture 8 during the windowing process, reaches the beam splitter 9, and is then reflected by the third reflecting mirror 10 into the galvanometer 11 and telecentric field mirror 12, and is focused on the positive focal plane 15 for the windowing process. Then, the beam passing through the one-dimensional AOD 3 is deflected by the one-dimensional AOD 3, causing the beam to propagate on another optical path. Thus, the beam first passes through the first reflecting mirror 4 in the other optical path, then through the second pinhole aperture 5, then through the concave lens 6 to change the divergence angle, and then through the second reflecting mirror 7 to reach the beam splitter 9. The light is reflected by the third reflecting mirror 10, enters the galvanometer 11 and telecentric field mirror 12, and is finally focused on the processed product for the adhesive removal process to achieve micro-via processing.

[0021] In summary, in actual blind hole laser processing, the standard processing method generally adopts a timing control of "windowing first, then adhesive removal". Windowing is the T1 stage and adhesive removal is the T2 stage. The AOD acousto-optic deflection system sets the corresponding frequency parameters in the T1 and T2 stages respectively to achieve precise switching of the beam path during the processing. This allows one beam to be used for the windowing process without beam shaping, while the other beam is used for the adhesive removal process by changing the divergence angle through a lens via a different path.

[0022] Figure 2 This is a schematic diagram of the internal structure and working principle of the AOD. J1 and J2 represent the two amplifier electrical signal input pins of the AOD. By controlling the application of different electrical signals, the acousto-optic deflector (AOD) can generate a positive phase difference (+ph) or a negative phase difference (-ph) when working at low or high frequencies of ultrasound, driving the acousto-optic crystal to deflect to the left or right, thereby changing the direction of the emitted light. At the center frequency, the acousto-optic crystal does not deflect and there is no phase difference.

[0023] The first pinhole aperture 8 and the second pinhole aperture 5 are perpendicular to the beam, and their aperture diameters are adjustable. The central axis of the aperture of the one-dimensional AOD3 coincides with the optical path. Adjusting the incident angle improves the +1st order diffraction efficiency, allowing the outgoing beam to follow any trajectory on the one-dimensional plane. The second reflector 7 and the third reflector 10 are at 45° to the incident and reflected beams, respectively. The incident aperture of the galvanometer 11 is perpendicular to the incident beam, and the exit aperture is perpendicular to the outgoing beam. The telecentric field mirror 12 is connected to the exit aperture of the galvanometer 11 via a thread.

[0024] This invention employs one-dimensional AOD (Acousto-optical deflection) technology to alter the path of the second beam of light, thereby using a lens along that path to correct the divergence angle. This process sequentially processes the material, achieving the goal of creating a blind hole in one step.

[0025] This system has the following characteristics:

[0026]

[0027] Table 1

[0028] As shown in Table 1, the AOD acousto-optic defocusing processing system improves efficiency by 14% to 44% compared to dual-laser and single-laser processing systems, while stability is improved by 98% compared to dual-laser processing systems, as indicated by the blind hole yield rate, which is higher than that of dual-laser processing systems.

[0029] This invention can replace mechanical defocusing of the galvanometer, reduce mechanical movement during processing, and improve processing efficiency;

[0030] It can overcome the problem of unstable optical path of dual lasers and improve the stability of the equipment;

[0031] Replacing dual lasers with one-dimensional AOD can ensure that the parameters of the two beams are completely consistent, reduce debugging operations, and ensure the safety of product processing;

[0032] No mechanical movement is required within the galvanometer's processing range, improving positioning and processing accuracy.

[0033] Compared to dual-laser systems, this reduces costs;

[0034] In conventional galvanometer systems, changing the focal height of a laser beam can only be achieved by altering the z-axis height or using dual lasers. Changing the z-axis height is relatively stable, but the laser cannot function due to mechanical movement, affecting processing efficiency. In dual-laser systems, one laser is focused while the other is defocused. The two beams are combined into a single beam and applied to the product. By processing sequentially, blind holes can be completed in one go, resulting in high efficiency. However, the beam-combining effect is highly unstable due to mechanical stress and vibration. Acousto-optic deflectors control the crystal refractive index via acoustic frequency, thereby changing the beam propagation angle. By setting a one-dimensional AOD (Aspect-Oriented Deflector) to emit light sequentially at two deflection angles and adjusting the divergence angle of one beam, the two beams are combined to perform blind hole processing on the material in one go. This method not only eliminates the delay caused by mechanical means but also ensures the stability of the processing effect.

[0035] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization, characterized in that: The system includes a laser (1) and optical path devices. A zoom beam expander (2) is provided at the exit of the laser (1). A one-dimensional aperture (AOD) (3) is provided behind the zoom beam expander (2). The beam passing through the one-dimensional AOD (3) passes through the first aperture stop (8) and reaches the beam splitter (9). Then, it is reflected by the third mirror (10) and enters the galvanometer (11) and the telecentric field mirror (12), and is focused on the positive focal plane (15) for the windowing process. The beam passing through the one-dimensional AOD (3) The beam is then deflected by a one-dimensional AOD (3) so that it propagates on another optical path. The beam then passes through the first reflecting mirror (4) in the other optical path, through the second small aperture (5), through the concave lens (6) to change the divergence angle, and then through the second reflecting mirror (7) to reach the beam splitter (9). After being reflected by the third reflecting mirror (10), it enters the galvanometer (11) and the telecentric field mirror (12) and is finally focused on the processed product to achieve micro-hole processing.

2. The laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization as described in claim 1, characterized in that: The first pinhole aperture (8) and the second pinhole aperture (5) are perpendicular to the light beam, and the aperture diameter can be adjusted.

3. The laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization as described in claim 1, characterized in that: The central axis of the light-transmitting aperture of the one-dimensional AOD(3) coincides with the optical path.

4. The laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization as described in claim 1, characterized in that: The second reflector (7) and the third reflector (10) are at 45° to the incident beam and the reflected beam, respectively.

5. The laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization as described in claim 1, characterized in that: The incident aperture of the galvanometer (11) is perpendicular to the incident beam, and the exit aperture is perpendicular to the exit beam.

6. The laser processing system for improving the efficiency of blind vias in PCBs based on AOD polarization according to claim 1, characterized in that: The telecentric field mirror (12) and the galvanometer (11) exit hole are connected by threads.

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