电镀金刚线硅片切割废料杂质溯源及源头控制

Impurity Traceability and Source Control of Diamond Wire Silicon Wafer Cutting Waste

随着中国光伏产业快速发展,单晶硅片需求和产量逐年增加,金刚线硅片切割废料产量随之急剧增加,不仅导致高纯硅资源浪费,还造成严重生态环境问题。硅片切割过程中35%~40%的99.9999%的高纯硅(6N级)生成亚微米硅粉损失,且随着细线化、薄片化等金刚线硅片切割工艺的进步,废料杂质来源变得复杂和多样,增加提纯回收增值利用难度。为了降低回收难度,科学合理制定回收工艺路线、研发高效清洁回收技术以期获得易循环再生的高纯硅废料,进行杂质溯源研究明确其来源及渠道,以通过源头控制实现原料质量的稳定和提升对废料回收利用极为必要。结合单晶硅片切割工艺,基于典型原料分析结果,通过对切片过程相关辅料进行采样和分析,完成硅片切割废料中的杂质溯源研究,并提出了有效的源头控制措施,获得了高品质的原料。结果表明:Al杂质来源于有机添加剂和垫板,Fe和Ni杂质来源于金刚线,Ca杂质来源于工业用水和粘胶,Mg杂质来源于有机添加剂和工业用水,有机C来源于垫板和粘胶。源头控杂后得到的硅片切割废料中Al,Fe及Ca杂质含量大幅下降,分别为1.3×10^(-6),4.3×10^(-6)和5.5×10^(-6)。对硅片切割废料杂质源头控制提升原料品质和提高废料利用效率具有重要意义。

With the rapid development of China's photovoltaic industry,the demand and output of monocrystalline silicon wafers have increased year by year,and the output of diamond wire silicon wafer cutting waste has increased dramatically,which not only leads to the waste of high-purity silicon resources,but also causes serious ecological and environmental problems.In the process of silicon wafer cutting,35%~40%of 99.9999%(6N) grade high purity silicon is lost to submicron silicon powder.With the progress of diamond wire silicon wafer cutting process,such as fine line and flake,the source of waste impurities becomes complex and diverse,with significant characteristics such as species diversity,content fluctuation and oxidation difference,which increases the difficulty of purification,recovery and value-added utilization.The key reason is that the source of impurities in photovoltaic silicon wafer cutting waste is untraceable.The existing research has not carried out impurity traceability and source control to improve the quality of raw materials,and lacks effective recovery process,which directly leads to the purity of recovered silicon unable to meet the requirements of photovoltaic silicon,thus seriously restricting the industrial application of photovoltaic silicon wafer cutting waste recycling to prepare single crystal silicon.In order to reduce the difficulty of recycling,scientifically and rationally formulate the recycling process route,develop efficient and clean recycling technology,and obtain high-purity silicon waste that is easy to recycle,it is necessary to carry out impurity traceability research to clarify its source and channel,so as to achieve the stability and improvement of raw material quality through source control.In this paper,based on the analysis results of typical raw materials,combined with the single crystal silicon wafer cutting process,the potential impurity source samples such as diamond wire,pad,brush-coated viscose,organic additives and industrial water consumed in a silicon wafer cutting cycle and the waste slurry matched with the potential impurity source samples in this silicon wafer cutting cycle were collected.By inductively coupled plasma atomic emission spectrometry (ICP-AES),scanning electron microscopy (SEM-EDS),electron probe microanalyzer (EPMA),X-ray fluorescence spectrometer (XRF),organic element analyzer(EA) and X-ray diffraction (XRD) and other means.The potential impurities in the auxiliary materials and the unfavorable factors causing impurities in the cutting process were systematically analyzed,and the research on the traceability of impurities in the silicon wafer cutting waste was completed.In addition,effective source control measures were proposed for the source of impurities in silicon wafer cutting waste,and the effectiveness of these measures was verified by experiments,and high-quality raw materials were obtained.The results showed that in the process of diamond wire cutting silicon wafer,Al,Fe,Ni,Ca,Mg impurities and C impurities were introduced from the outside during the cutting process.Al impurities were mainly derived from the organic additives used in cutting and the auxiliary material backing plate for fixing the silicon ingot.Fe and Ni impurities were derived from the friction and shedding of the coating on the surface of the diamond wire during the cutting process,and the content of these two impurities in the silicon wafer cutting waste was high due to the influence of the wire changing frequency during the cutting process.Ca impurity came from industrial water and brush-coated viscose,and Mg impurity came from organic additives and industrial water.The main reason was that the reuse of industrial water led to the cumulative increase of Ca and Mg impurities,and organic C element was mainly derived from amorphous material pads and organic viscose.Through traceability research,the specific source of impurities was clarified,and corresponding control measures were proposed for the source of impurities.Through the proposed source impurity control measures,the quality of waste was taken into account,and the matching slicing process could be optimized to reduce the number of impurities brought into the diamond wire and water-based coolant.Optimizing auxiliary materials and promoting the realization of impurity-free slicing at the source could reduce the pollution of waste impurities Fe,Ni and C elements.The purification of circulating water to reduce the accumulation of impurity ions could remove the influence of Ca and Mg impurities.The introduction of impurity Al and Mg elements could be controlled by eliminating the secondary pollution of impurities without flocculation or flocculant without hybridization,and high-quality raw materials were obtained by source impurity control measures.The contents of Al,Fe and Ca impurities in the silicon wafer cutting waste were1.3×10^(-6),4.3×10^(-6) and 5.5×10^(-6),respectively,and the impurity content was greatly reduced,which proved the effectiveness of source control impurities.This study clarified the source of impurities,and solved the adverse factors that cause the introduction of impurities from the source through the control of impurity elements.It was of great significance to ensure the quality of raw materials for silicon wafer cutting waste,promote the recovery of silicon purity added value and improve the utilization efficiency of waste.