Study on cutting PV polysilicon with a new type of diamond abrasives-helix-distribution saw wire based on controlling the subsurface microcrack damage depth

Abstract

There are large brittle fracture pits on the surface of photovoltaic polysilicon wafer cut by diamond wire saw, because of the problems such as poor flow of cutting fluid and difficulty in chip discharge. At the same time, the anti-corrosion amorphous layer on the wafer surface can obviously block the subsequent acid etching and texturing reaction. In order to solve these problems, a new type of diamond abrasives-helix-distribution saw wire is used as the sawing tool to obtain the surface characteristics of photovoltaic polysilicon wafer suitable for acid texturing, then research on wire sawing photovoltaic polysilicon based on controlling subsurface microcrack damage depth control is carried out. The concept of high-quality cutting abrasives (HQCA) is defined, and the cutting process of polycrystalline silicon is numerically calculated based on the established new type diamond wire model, the influence of the process parameters and the structural parameters of the saw wire on the cutting characteristics is analyzed, and the reasonable matching between the process parameters and the saw wire parameters is discussed. The study results show that the number and proportion of HQCA in all abrasive grains involved in sawing can be increased by increasing the workpiece feed speed or reducing the moving speed of saw wire, properly reducing the abrasive concentration on the saw wire surface or increasing the abrasives size, or setting the ratio of axial distance between the abrasive area on wire surface and the bare wire area as 1:1. In this case, the formation of the wafer surface tends to be removed in the way of material microbrittleness, and the subsurface crack depths are in the optimal etching depth range. The number and proportion of HQCA remain basically unchanged when the workpiece feed speed changes in constant proportion to the wire speed, and the screw pitch of the abrasive groups on the surface of the saw wire has little effect on it.