Impurity Traceability and Source Control of Diamond Wire Silicon Wafer Cutting Waste
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 sili-con wafer cutting,35％～40％of 99.9999％(6N)grade high purity silicon is lost to submicron silicon powder.With the progress of dia-mond 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 puri-fication,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 materi-als,and lacks effective recovery process,which directly leads to the purity of recovered silicon unable to meet the requirements of pho-tovoltaic silicon,thus seriously restricting the industrial application of photovoltaic silicon wafer cutting waste recycling to prepare sin-gle crystal silicon.In order to reduce the difficulty of recycling,scientifically and rationally formulate the recycling process route,de-velop 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 wa-fer cutting process,the potential impurity source samples such as diamond wire,pad,brush-coated viscose,organic additives and in-dustrial 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 ob-tained.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 cut-ting 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 con-trol 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 dia-mond 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 materi-als were obtained by source impurity control measures.The contents of Al,Fe and Ca impurities in the silicon wafer cutting waste were 1.3×10-6,4.3×10-6 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 wa-fer cutting waste,promote the recovery of silicon purity added value and improve the utilization efficiency of waste.
silicon wafer cutting wastehigh purity silicon recoverytraceability of impuritiessource control
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