Diamond wire loop cropping VS Band saw cropping
Diamond wire loop has a advantage position in the processing of silicon wafers, where exactly?
First, the processing technology of silicon wafers is introduced.
Silicon wafers are generally divided into monocrystalline silicon wafers and polycrystalline silicon wafers. The preparation of silicon wafers is divided into the production process and processing technology of monocrystalline silicon and polycrystalline silicon.
The manufacturing steps involved in the wafer processing process vary by wafer manufacturer.
(1) Single crystal silicon wafer processing technology
Cropping → OD rounding → slicing → chamfering → grinding → corrosion, cleaning, etc.
①Cropping: After the crystal growth is completed, cut off the useless parts of the crystalline silicon head and tail along the direction perpendicular to the crystal growth.
②Outer diameter rounding: In Czochralski monocrystalline silicon, due to thermal vibration and thermal shock during crystal growth, the crystal surface is not very smooth, that is to say, the diameter of the entire monocrystalline silicon fluctuates to a certain extent;
In addition, there are flat ridges on the surface of the single crystal silicon rod after the crystal growth is completed, and further processing is required to make the diameter of the entire single crystal silicon rod uniform. For ease of operation in subsequent materials and processing processes.
③ Slicing: After the single crystal silicon spheronization process is completed, the single crystal silicon rod needs to be sliced. When slicing single crystal silicon for solar cells, the parameters such as the crystal orientation, parallelism and warpage of the silicon wafer are not high, and only the thickness of the silicon wafer needs to be controlled.
④Chamfering: The single crystal silicon rod is cut into wafers, and the sharp edge of the wafer needs to be trimmed into an arc shape, mainly to prevent the edge of the wafer from cracking and lattice defects.
⑤ Grinding: After slicing, line marks are generated on the surface of the silicon wafer. It is necessary to remove the saw marks and surface damage layer caused by the slicing by grinding, which can effectively improve the warpage, flatness and parallelism of single crystal silicon, and achieve a polishing process.
⑥Corrosion and cleaning: After slicing, there is a mechanical damage layer on the surface of the silicon wafer, the crystal lattice near the surface is incomplete, and the surface of the silicon wafer is contaminated with impurities such as metal particles.
Therefore, after generally slicing, before preparing the solar cell, the silicon wafer needs to be chemically corroded. Cleaning is required in many steps in the processing of single crystal silicon wafers, and the cleaning here is mainly the final cleaning after corroding. The purpose of cleaning is to remove all sources of contamination from the wafer surface.
(2) Polycrystalline silicon wafer processing technology
Squaring → grinding → chamfering → slicing → corrosion, cleaning, etc.
①Squaring ：For the square crystalline silicon ingot, after the silicon ingot is cut, it needs to be cut into squares, that is, along the longitudinal direction of the crystal growth of the silicon ingot, the silicon ingot is cut into rectangular silicon blocks of a certain size.
②Grinding surface: Line marks will be produced on the surface of the silicon block after squaring, requires grinding to remove saw marks and surface damage from squaring, effectively improve the flatness and parallelism of the silicon block to achieve a polishing process.
③Chamfering: After the polysilicon is cut into silicon blocks, the sharp corners of the silicon block need to be chamfered and trimmed into an arc shape, mainly to prevent the edge of the silicon wafer from cracking, chipping and lattice defects during cutting.
The slicing and subsequent corroding and cleaning processes are almost the same as those of single-crystal silicon, and will not be repeated here.
To sum up, whether it is single crystal silicon wafer processing or polycrystalline silicon wafer processing, there are two main processes of cropping and slicing.
In most silicon wafer fabrication technologies, the diamond wire is sliced after being cut by a conventional band saw.
The diamond wire saw mentioned here is a diamond wire specially designed for cutting silicon wafer. This wire is very thin, about 0.03mm. It can cut the crystal into thin slices. It should be noted that it cannot be used for cropping.
The cropping blade of the band saw is thick and easy to operate, but the knife seam is wide, which wastes materials and causes serious damage to the surface of the silicon wafer.
The wire diameter of the diamond wire saw is relatively small and cannot directly cut the cryster.
And we have developed an diamond wire loop, which is a relatively thick diamond wire that can be used to cut cryster. Compared with the band saw, the cutting speed is faster, the knife seam is smaller, the material is saved, and the cutting precision is higher. Can replace band saw cropping.
Here is the silicon cropping video:
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