Method for reducing taper angle of ultrafast laser etching micro through hole through back reflection condensation

Abstract

The invention provides a method for reducing the taper angle of an ultrafast laser etching micro through hole through back reflection condensation. A device used in the method mainly comprises a power supply unit, an ultrafast laser machining unit, a computer control unit, a precise displacement unit and a back reflection condensation unit. The ultrafast laser processing unit is used for etching the micro through hole; the computer control unit is used for regulating and controlling laser parameters and realizing the displacement of the workpiece by controlling the precise displacement unit; the back reflection light condensation unit is used for achieving coaxial and concentric adjustment of the through hole and the concave reflector, through the concave reflector arranged on the back face of the workpiece, a penetrating incident laser beam is recycled, reflected and accurately focused to an outlet of the through hole again, and the through hole is etched while the micro through hole is etched in the front face. Synchronous, efficient and precise etching and removal of hole outlet and tail materials are realized; the method is simple, practical, low in cost and high in applicability, single-time adjustment, single-face machining and double-face simultaneous forming of ultrafast laser are conveniently achieved, taper angle reduction and back face reaming are remarkable, and therefore the hole forming quality and efficiency are greatly improved.

Description

Technical Field

[0001] The invention relates to the field of laser drilling, and in particular to a method for reducing the cone angle of a micro-through hole etched by ultrafast laser by back reflection and focusing. Background Art

[0002] With the rapid development of science, technology and industry, the demand for micro-through-hole structures in the fields of aerospace, automobile, optoelectronics and medical equipment industries is increasing. Ultrafast laser etching micro-hole technology has been widely used due to its advantages such as high peak power, high power density and wide range of processing materials. However, the laser beam itself has diffraction and divergence effects, and the laser beam usually undergoes multiple reflections, refractions and scattering between the hole walls in the hole, which leads to the continuous attenuation of the laser beam energy along the hole depth direction, the continuous deterioration of the laser beam self-focusing ability, the continuous attenuation of the laser beam energy and power density, and the problems of axial defocusing and radial defocusing.

[0003] Due to the above reasons, in the process of ultrafast laser etching of micro-vias, the dimensional deviation between the entrance and exit of the etched micro-vias is usually large, that is, a tapered hole is usually etched. Micro-vias with large tapers may cause performance degradation or even failure of precision components. Therefore, it is urgent to design and invent a new method that is simple, practical, low-cost, highly applicable, and can significantly reduce the taper angle of ultrafast laser-etched micro-vias, so as to accurately and efficiently expand the back of the micro-vias, effectively solve the taper angle problem encountered in the process of ultrafast laser etching of micro-vias, and greatly improve the quality and efficiency of hole making. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for reducing the taper angle of a micro-through hole in ultrafast laser etching by back-reflection focusing. The method realizes coaxial and concentric adjustment of a concave reflector and a through hole through precise displacement of a three-dimensional precision displacement slide, and recovers the incident laser beam entering the through hole for reuse and reflection through a concave reflector placed on the back of the workpiece, and refocuses the beam to the through hole outlet accurately. While etching the micro-through hole from the front, simultaneous efficient and precise etching and removal of the hole outlet and the tail material are realized, thereby increasing the aperture of the micro-through hole outlet and reducing the taper angle of the micro-through hole.

[0005] The method for reducing the taper angle of ultrafast laser-etched micro-through holes by back-reflection focusing comprises the following steps: The first step is to place the optical bracket with the concave reflector on a three-axis precision shift slide, and adjust the three-axis precision shift slide to achieve coaxial and concentric adjustment of the concave reflector and the position of the through hole to be processed on the workpiece; The second step is to adjust the three-axis precision shift slide to keep the relative distance between the concave reflector and the lower surface of the workpiece at twice the focal length of the concave reflector; The third step is to adjust the laser parameters through the computer control unit and control the precision shift unit to move the workpiece to the preset position; The fourth step is to turn on the ultrafast laser processing unit. The laser beam is irradiated through the laser head to the position to be processed on the upper surface of the workpiece and etches the micro-through hole. After ultrafast laser perforation, the perforating laser beam continues to etch. At this time, the concave reflector placed on the back of the workpiece will recycle the perforating incident laser beam and reflect it back to the through-hole exit to achieve synchronous, efficient and precise etching and removal of the hole exit and tail material.

[0006] The method for reducing the cone angle of ultrafast laser-etched micro-through holes by back-reflection focusing also relates to a laser-etched micro-through hole device, which includes a power supply unit, an ultrafast laser processing unit, a laser head, a workpiece, a computer control unit, a precision shift unit and a back-reflection focusing unit.

[0007] The computer control unit is used to adjust the laser parameters and realize the displacement of the workpiece by controlling the precision shift unit; the ultrafast laser processing unit is used to etch micro-through holes; the back-reflection focusing unit includes an optical bracket, a concave reflector, a three-axis precision shift slide and a support platform; the concave reflector is placed on the optical bracket, the optical bracket is connected to the three-axis precision shift slide by bolts, the three-axis precision shift slide is connected to the precision shift platform by bolts, and the support platform is placed on the precision shift platform by welding; the back-reflection focusing unit is used to realize the coaxial and concentric adjustment of the through hole and the concave reflector, and through the concave reflector placed on the back of the workpiece, the perforating incident laser beam is recycled and reused and reflected and re-focused to the through hole outlet, so that while etching the micro-through hole on the front side, the hole outlet and the tail material are synchronously and efficiently etched and removed.

[0008] Preferably, a workpiece clamping device is provided on the support platform to prevent the workpiece from shifting during processing.

[0009] Preferably, the concave surface of the concave reflector is coated with a protective silver film to improve the reflectivity of the light beam.

[0010] Preferably, the precision shifting platform can realize precision shifting in two horizontal axis directions, and is used to realize horizontal precision shifting of the workpiece.

[0011] Beneficial effects of the present invention: The present invention provides a method for reducing the taper angle of a micro-through hole etched by ultrafast laser by back-reflection focusing. The method is suitable for ultrafast laser micro-through hole processing. By placing a concave reflector on the back of a workpiece, the incident laser beam for perforation is recovered and reused and reflected and re-focused accurately to the through hole outlet. While etching the micro-through hole on the front side, synchronous efficient and precise etching and removal of the hole outlet and tail material are achieved. The method is simple and practical, low in cost, and highly applicable. It is easy to achieve single-time adjustment of ultrafast laser, single-sided processing and double-sided simultaneous forming, and can significantly increase the aperture of the micro-through hole outlet and significantly reduce the taper angle of the micro-through hole, thereby greatly improving the hole making quality and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic structural diagram of the laser etching micro-through hole device involved in the present invention.

[0013] Figure 2 The figure is a schematic diagram of the laser reflection and focusing principle involved in the present invention.

[0014] In the figure: 1—power supply unit; 2—ultrafast laser processing unit; 3—laser head; 4—workpiece; 5—computer control unit; 6—precision shift platform; 7-1—optical bracket; 7-2—concave reflector; 7-3—three-axis shift slide; 7-4—support platform. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0016] The method for reducing the cone angle of ultrafast laser etching micro-through holes by back-reflection focusing described in the present invention comprises the following steps: The first step is to place the optical bracket 7-1 with the concave reflector 7-2 on the three-axis precision shift slide 7-3, and adjust the concave reflector 7-2 and the position of the through hole to be processed on the workpiece 4 by adjusting the three-axis precision shift slide 7-3. The second step is to adjust the three-axis precision shift slide 7-3 so that the relative distance between the concave reflector 7-2 and the lower surface of the workpiece 4 is maintained at twice the focal length of the concave reflector 7-2; The third step is to adjust the laser parameters through the computer control unit 5 and control the precision shift unit 6 to move the workpiece 4 to the preset position; The fourth step is to turn on the ultrafast laser processing unit 2, and the laser beam is irradiated to the position to be processed on the upper surface of the workpiece through the laser head 3 and etches the micro-through hole; after ultrafast laser perforation, the perforating laser beam continues to etch, and at this time, the concave reflector 7-2 placed on the back of the workpiece 4 will recycle the perforating incident laser beam for reuse and reflect it and refocus it precisely to the through-hole exit, so as to realize the synchronous, efficient and precise etching and removal of the hole exit and the tail material.

[0017] like Figure 1 The figure shows a laser through-hole etching device involved in the present invention, which includes a power supply unit 1, an ultrafast laser processing unit 2, a laser head 3, a workpiece 4, a computer control unit 5, a precision shift unit 6 and a back reflection focusing unit 7. The computer control unit 5 is used to adjust the laser parameters in the ultrafast laser processing unit 2 and realize the precise displacement of the workpiece 4 in the horizontal two-axis direction by controlling the precise displacement unit 6; the ultrafast laser processing unit 2 is used to etch micro-through holes; the back reflection focusing unit 7 includes an optical bracket 7-1, a concave reflector 7-2, a three-axis precise displacement slide 7-3 and a support platform 7-4, wherein, in order to improve the reflectivity of the light beam, a concave reflector 7-2 with a protective silver film coated on the concave surface is used and placed on the optical bracket 7-1, the optical bracket 7-1 is connected to the three-axis precise displacement slide 7-3 by bolts, the three-axis precise displacement slide 7-3 is connected to the precise displacement platform 6 by bolts, and in order to prevent the workpiece 4 from shifting during the processing, a workpiece clamping device is provided on the support platform 7-4, and the support platform 7-4 is placed on the precise displacement platform 6 by welding.

[0018] like Figure 2 The figure shows the laser reflection and focusing principle involved in the present invention. Based on the coaxial and concentric adjustment of the through hole and the concave reflector 7-2, the incident laser beam of the perforation is recovered and reflected and re-focused precisely to the through hole outlet through the concave reflector 7-2 placed on the back of the workpiece 4. While etching the micro-through hole on the front side, the hole outlet and the tail material are simultaneously and efficiently etched and removed, thereby increasing the aperture of the through hole outlet, significantly reducing the through hole taper angle, and greatly improving the hole forming quality.

[0019] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for reducing the taper angle of ultrafast laser etching micro-through holes by back reflection focusing, characterized in that: The following steps are involved: The first step is to place the optical support (7-1) with the concave reflector (7-2) on a three-axis precision shift slide (7-3), and to adjust the concave reflector (7-2) and the position of the through hole to be processed on the workpiece (4) by adjusting the three-axis precision shift slide (7-3); The second step is to adjust the three-axis precision shift slide (7-3) so that the relative distance between the concave reflector (7-2) and the lower surface of the workpiece (4) is maintained at twice the focal length of the concave reflector (7-2); The third step is to adjust the laser parameters through the computer control unit (5) and control the precision shift unit (6) to move the workpiece (4) to a preset position; The fourth step is to start the ultrafast laser processing unit (2), and the laser beam is irradiated to the position to be processed on the upper surface of the workpiece through the laser head (3) and etches the micro-through hole; after the ultrafast laser perforation, the perforation laser beam continues to etch, and at this time, the concave reflector (7-2) placed on the back of the workpiece (4) will recycle the perforation incident laser beam and reflect it and refocus it accurately to the through hole exit, so as to achieve synchronous, efficient and precise etching and removal of the hole exit and tail material.

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