光伏多晶硅游离-固结磨粒复合线锯切片技术及机理研究

At present, there exist protruding problems such as difficult surface texturing, risk of slice fragmentation and wire saw breaking in fixed abrasive wire saw slicing polycrystalline silicon solar cell. This project proposes research of free and fixed abrasive combined wire saw slicing photovoltaic polysilicon technology and mechanism, with obtaining the easy texturing surface as the study topic, by combining the advantages of free and fixed abrasive wire saw technology. The free and fixed abrasive combined wire saw slicing, which aims to improve the surface micromorphology and fracture strength of the silicon wafer, is to use the grits-spiral-distribution electroplated wire saw as the main sawing tool to carry out the main sawing effect, and use the spiral microspace between the surface of the wire saw and the silicon wafer to restrain the free abrasives in the slurry then to achieve the surface lapping effect of silicon wafer. This proposal focuses on clarifying the mechanism of material removal and surface generation in the new combined sawing process, characterization of surface/subsurface properties of polysilicon slices and revealing the mechanism and regularity of its influence on the surface texturing and fracture strength of silicon slices; and revealing the wafer fragmentation mechanism then putting forward the corresponding control measures; finally, providing the optimized sawing process and parameters to form of the systematic basic theory and technology of wire saw combined machining. The research results will provide a new way of thinking for the slicing process of photovoltaic polysilicon and open up a new way, which has important theoretical value and application prospect.

目前固结磨粒线锯切割多晶硅太阳能电池片时存在表面制绒难、易碎片、断线等突出问题，本项目以结合游离与固结磨粒线锯切割工艺各自优势为基本思想，以获得易制绒的多晶硅切片表面为研究主题，提出光伏多晶硅游离-固结磨粒复合线锯切片技术及机理研究。以表面磨粒群螺旋排布锯丝为主体锯切工具，实施主要锯切作用，以锯丝与硅片表面之间的螺旋微空间约束砂浆中的游离磨粒，对硅片表面进行辅助研磨作用，形成游离-固结磨粒复合线锯切割，改善硅片表面微观形貌和断裂强度。阐明新锯切工艺的材料去除机理和表面创成机理，表征多晶硅切片表面/亚表面特性，揭示其对硅片制绒效果和断裂强度的影响机制及规律；揭示硅片破碎机制，提出相应控制措施；提供优化的锯切工艺及参数组合，形成系统的多晶硅电池片复合线锯切割的基础理论和工艺技术。研究成果为光伏多晶硅的切片加工提供了新的思路，开拓了新的途径，具有重要的理论价值和应用前景。

中国已成为全球最大的光伏制造和加工基地。目前近90%的太阳能电池采用的是硅晶片，而多晶硅电池在光伏市场中占相当大比例。切片加工是多晶硅电池片制造工艺中第一道工序，加工质量对电池片后续制绒工艺、破碎率等方面有重要的影响。针对金刚线切割技术切割多晶硅太阳能电池片时存在表面制绒难、易碎片等突出问题，本项目提出了光伏多晶硅游离-固结磨粒复合线锯切片技术。研究了复合线锯切割机理、硅片表面创成机理、硅片表面/亚表面加工特性、制绒特性、断裂强度等方面研究，形成了较系统的复合线锯切割理论体系。研究工作为光伏多晶硅的切片加工提供了新的思路，开拓了新的途径。.开展了固结-游离磨粒复合线锯加工的砂浆流体动压效应研究，研究了切削区成膜状态和流体动压力，分析了各因素对切削区膜厚与压力分布的影响规律。仿真了切削冷却液流场，研究了锯切区域中冷却液的运动特性和磨粒分布状态，获得了各参数对其的影响关系。研究了游离磨粒力学行为，分析了切削区游离磨粒的运动情况和冷却液的流动状态对切片表面形貌的影响规律。通过理论与试验研究，揭示了游离磨粒与固结磨粒的综合切削作用，揭示了复合线锯的锯切机理和切片表面创成机理。探究了多晶硅片的机械性能与酸制绒后的减反性能，构建了工艺参数、硅片表面/亚表面特征与制绒特性之间的联系。建立了硅片表面粗糙度、波纹度和亚表面微裂纹损伤特征理论预测模型，构建了锯丝参数与工艺参数对硅片表面/亚表面特性的影响规律。建立了基于半饼状裂纹系统的线锯切割硅片断裂强度数值分析模型，得出了工艺参数、锯丝参数以及亚表面微裂纹损伤深度与硅片断裂强度之间的关系。建立了锯切中硅片受迫振动稳态解数值模型，确定了确定加工工艺参数下的硅片破碎概率。分别建立了多晶硅锭装夹和锯切加工过程的有限元仿真模型，确定了加工动态应力场分布状态。