半导体材料电火花线切割往复渐进式自适应进给控制研究

According to the requirement of high efficiency and high accuracy cutting of semiconductor materials, the inner diamond slicing and multi-wires sawing methods is analyzed and a novel type of feed motion called reciprocating progressive adaptive feed (RPAF) motion is proposed. Traditionally, feed mechanism only moves one-way along the CNC programmed path, while the new type of feed motion breaks through the traditional way and it is able to solve the question that it is hard to control the feedrate during the machining of semiconductor by wire electrical discharge machining because of the special electrical properties of semiconductor materials. Four aspects of research work, including feed drive system design, complex trajectory generation, adaptive adjustment of feed parameters and decoupling control for multi-wires electrical discharge machining, are going to be carried out and a RPAF control theory and technology system is going to be built. Two adaptive control methods are proposed, one is the motion-perception based method for adjusting the range and frequency of reciprocating feed motion, the other is the method for adjusting the feedrate, which is based on the multi-input predictive model on the eroding speed and the artificial-neural-networks iterative optimization mechanism. On the basis of that, the realizing of the RPAF for the multi-wires electrical discharge machining system is planned to be studied by means of vision image analysis and modeling of electrical field, heat field and force field coupling and coordination control of electrode wire movement and feed motion. The research achievement is able to provide a prototype and key technical support for the successive development of multi-wires electrical discharge machine tools for semiconductor materials machining with low cost, high efficiency, high adaptability, high materials utilization factor and independent intellectual property, thus the technologies of both electrical discharge machining and semiconductor manufacturing can be promoted.

针对半导体材料高效高精度切割加工需求，在分析内圆切割法与多线研磨切割法存在的问题的基础上，打破进给机构按照数控程序编制路径单向进给的传统，提出全新的往复渐进自适应进给运动方式，解决半导体材料因电学性质特殊在电火花线切割过程中进给速度难以控制的问题。从进给驱动系统设计、复杂轨迹生成、进给参数自适应调节与多线切割解耦控制四个方面深入研究，构建往复渐进自适应进给控制的理论与技术体系。提出基于运动感知调节往复运动幅度与频率以及基于蚀除速度多输入预测模型与人工神经网络滚动优化调节进给速度的自适应控制方法。在此基础上，研究通过视觉图像分析、电热力多场耦合建模以及走丝与进给协调控制等途径实现电火花多线切割系统的往复渐进式自适应进给控制。研究成果可为成功研制具有自主知识产权的低成本、高效率、高适应性、高材料利用率的半导体材料电火花多线切割机提供样机与关键技术支撑，提升我国电火花加工与半导体制造的技术水平。

硅、锗等半导体材料的切割是太阳能电池与集成电路芯片制造过程中最重要的环节之一。使用电火花线切割方法可以有效克服半导体材料因为具有硬脆性而难以用常规机械方法加工的问题。但是，由于半导体材料的特殊电学特性使传统用于金属切割的电火花线切割伺服控制系统失效，出现弯丝、断丝与切割效率低下等新问题。对此，提出了往复渐进式自适应进给控制方法，并开展了高精度脉冲插补、轨迹重叠反向插补、高速串行数据通信、模糊自适应控制等相关的运动控制技术应用基础研究。首先通过运动控制仿真深入分析了往复渐进自适应进给控制的原理，制订了相应的运动控制流程；然后通过对旧机床的改装设计建立了电火花线切割运动控制实验平台，自主开发了专用伺服控制系统，结合在线检测技术与预测控制、模糊控制理论对进给速度以及放电电流阈值等重要运动控制参数进行自适应调整。实验结果表明所提出的新方法切实有效，而且能够明显弱化切割面黑白相间的换向纹。在此基础上，针对单线切割效率低下的问题，研制了一台新型的并行放电多电极电火花线切割机，并针对其中的多线切割运丝机构设计、多电极放电电路建模、同步均衡放电与多电极丝解耦控制方法进行了深入研究，实现了稳定而高效的硅材料电火花多线切割，加工过程中无弯丝、断丝现象，三线切割的加工效率为单线切割效率的2.7倍。与目前广泛使用的机械研磨式线锯切割机相比，本项目所提出并研制的半导体材料电火花数控切割装备具有生产率高、成本低、切割损耗小、运行平稳、节能环保等优点。研究成果有助于巩固和发扬我国在电火花线切割领域的技术优势，推动我国太阳能光伏产业、集成电路制造业与数控系统技术的发展。