【摘要】 为实现孔径和锥度可调的微孔加工，设计研制了一种基于双振镜组联动与Z轴上下移动的五轴四联动激光旋切系统。建立了微孔激光旋切物理模型，首先利用边缘轮廓确定微孔形状，再通过分层回型填充方法确定每个激光作用点的位置；然后基于聚焦光束不被遮挡和振镜偏转整体运动量少的原则，确定四个振镜的偏转角度；通过改变边缘轮廓端点数据，可分别实现方孔尺寸和锥度的灵活可控。采用15 W紫外皮秒激光器、两套相同的振镜和焦距为32 mm的远心透镜，配合三维平移工作台，搭建了激光旋切硬件系统，自主开发了多边形激光旋切控制软件。实验采用分层降焦打孔的方式，在厚度为250μm的氮化硅材料上实现了55μm×55μm规格的正锥、零锥、负锥方形微孔的加工，并且还实现了不同孔径（30～80μm）零锥方形微孔和三角形、五边形、六边形等其他形状微孔的加工。更多还原

【Abstract】 Objective Micro-hole structures are widely used in devices such as aerospace turbine blades, automotive engine injector nozzles,and probe cards. With the improvement of the device performance requirements, the requirements of diameter and taper for microholes are also further raised. Conventional micro-hole processing methods include electrical discharge machining(EDM) and electrochemical machining(ECM). The shape of micro-hole cannot be precisely controlled by EDM, and the micro-hole machining precision is unsatisfactorily controlled by ECM. The general laser drilling methods include single-pulse drilling, multi-pulse drilling,and circular drilling. In all three drilling methods, the focusing position of beam is only controlled, but the beam incidence attitude is not controlled, and there were taper problems for the micro-hole. As an upgrade, the helical drilling can control the diameter and taper of micro-hole by precisely controlling the beam incident position and focusing orientation during the processing procedure. The research on helical drilling and related processing equipment is mainly aimed at the circular hole processing, and the irregular microhole processing still needs to be further studied. To obtain the square holes with adjustable tapers and controllable hole diameters on probe card materials, relevant studies and experiments are conducted in this study.Methods A new type of laser helical drilling system is presented. The system is composed of four-axis galvanometer groups controlled by linkage and Z axis moving device controlled independently. The processing plane is divided into two directions(X and Y directions) by double galvanometer groups, and the beam focusing position and incident orientation in each direction are controlled by two galvanometers. The physical model of micro-hole laser helical drilling is established. First, a coordinate system is applied to the micro-hole, and the shape of the micro-hole is determined by the edge profile. Second, the micro-hole is processed by a layer-by-layer filling method, while the laser focusing position is determined during processing. Third, the beam is controlled to shift in the opposite direction so that the focused beam is not blocked by the upper layer material during the process, and the minimum deflection motion of the galvanometer is required by optimizing the filling path. According to the above principles, the deflection angles of four galvanometers(X1, Y1 and X2, Y2) are determined. Finally, by changing the data of edge profile endpoint, the diameter and taper of micro-hole can be conveniently controlled.Results and Discussions In this study, a 15 W ultraviolet picosecond laser, two sets of identical galvanometers, a telecentric lens with a focal length of 32 mm, and a three-dimensional translation stage are used to build the laser helical drilling hardware system, and the polygon laser helical drilling control software is developed. The relevant experiments are completed on a 250 μmthick Si3N4 sample. The processing parameters are as follows: the power of the laser is 12 W, the repetition frequency is 50 kHz, the scanning speed of the galvanometer is 0.4 m/s, and the Z-axis movement speed is 2 mm/s. In the experiment, the taper of micro-hole is adjusted by changing the offset distance of the beam, and 55 μm×55 μm square micro-holes with positive taper, zero taper, and negative taper are achieved(Fig. 6). The cross sections of the hole wall are observed(Fig. 7). The beam offset distance for the square micro-hole with the zero taper is determined by the taper adjustment, and the 30-80 μm square micro-holes with zero taper are realized by adjusting the data of the edge profile endpoints(Fig. 8). Finally, by adjusting the number of profile endpoints to change the shapes of micro-holes, the triangular, pentagonal, hexagonal and other shapes of micro-holes are realized(Fig. 9).Conclusions In this study, a new type of laser helical drilling system is presented. The physical model of micro-hole laser helical drilling is established, in which the shape of the micro-hole is determined by edge contours and the laser focusing position is determined by the layer-by-layer filling method. The beam is controlled to shift in the opposite direction so that the focused beam is not blocked by the upper layer material during the process, and the minimum deflection motion of the galvanometer is required by optimizing the filling path. According to the above principles, and the deflection angles of four galvanometers(X1, Y1 and X2, Y2) are determined. Finally, by changing the edge profile endpoint data, the size and taper of micro-hole can be conveniently controlled. A 15 W ultraviolet picosecond laser, two sets of identical galvanometers, a telecentric lens with a focal length of 32 mm, and a threedimensional translation stage are used to build the laser helical drilling hardware system, and the polygon laser helical drilling control software is developed. By adjusting the processing parameters for relevant experiments, the micro-holes with different tapers under the same diameter and the micro-holes with the zero taper and different diameters are realized, and the micro-holes with different shapes are completed.更多还原