What is the main component of cutting fluid?

Because the surface smoothness, cleanliness, conductivity and other performance indexes of solar silicon wafer are extremely strict, silicon carbide micropowder with high hardness, small particle size and concentrated particle size distribution needs to be used as the main cutting medium in the cutting process of solar silicon wafer. In order to make the silicon carbide micropowder evenly dispersed in the cutting process and take away the huge friction heat generated in the cutting process in time, it is usually necessary to add the silicon carbide micropowder into the water-soluble or oily solar silicon wafer cutting liquid synthesized with polyethylene glycol (PEG) or oil as the main raw material in a certain proportion, and fully disperse it to make uniform and stable cutting mortar before it is used for silicon wafer cutting. Silicon carbide micropowder is used as the medium in the process of solar silicon wafer wire cutting. The whole mechanism is to use the hardness and sharp water chestnut of silicon carbide particles to make the silicon carbide micropowder particles continuously and rapidly impact the surface of the silicon rod and gradually cut off the silicon rod. This process will be accompanied by a lot of friction and heat release, and at the same time, the broken silicon carbide particles and silicon particles produced by the collision and friction between silicon carbide particles and silicon rods will also be mixed into the cutting system. In order to prevent the cut silicon wafer from warping due to the temperature increase of the cutting system and its surface from being excessively ground by fine particles, it is necessary to try to take the cutting heat and broken particles out of the cutting system in time. Therefore, the main function of the cutting fluid is to make the mortar have good fluidity, and the silicon carbide particles can be evenly and stably dispersed in the cutting system, and act on the surface of the silicon rod with a uniform and stable cutting force field during the high-speed movement of the steel wire, and at the same time take away the cutting heat and broken particles in time to ensure the surface quality of the silicon wafer.

The whole cutting process puts forward extremely high requirements and technical standards for the quality of cutting fluid for solar silicon wafers. As the solar silicon wafer cutting fluid is a compound mainly based on polyethylene glycol (PEG) or oil, it has good wettability, strong cutting ability and excellent dispersion characteristics for silicon carbide abrasives, and the performance characteristics of PEG play an irreplaceable role in the silicon wafer cutting fluid itself and the silicon wafer processing process. Polyethylene glycol (PEG): Also known as polyethylene glycol ether, it is produced by the step-by-step addition reaction of ethylene oxide with water or ethylene glycol, and its raw materials mainly come from petroleum products. Physical property: 1. When the molecular weight of PEG is 200-700, it is white or transparent viscous liquid; 1000-2000 is a waxy semi-hard solid; At 3000-20000, it is a hard waxy solid. Polyethylene glycol (PEG) is a low toxic and non-irritating polymer. 2. Relative density: liquid 65438. Solid1.17-1.215g/cm2; 3. Melting point: the solid is lower than 60℃ and the liquid is lower than 20℃; 4. Viscosity: 4.3-10.5x10-6m2/s (98.9℃); 5. The flash point is 179-252℃ (liquid) and 22 1-228℃ (solid). 6. Polyethylene glycol (PEG) has strong water absorption and can absorb water from the air at room temperature. The liquid can be miscible with water in any ratio. When the temperature rises, any fraction of solid polyethylene glycol can be miscible with water in any proportion. When the temperature reaches the boiling point of water, the polymer will precipitate, and the precipitation temperature depends on the molecular weight and concentration of the polymer. Chemical properties Polyethylene glycol (PEG) is a nonionic polymer, which is stable under normal conditions. At the temperature of 120℃ or higher, it can be oxidized by oxygen in the air under the protection of inert gases such as carbon dioxide or nitrogen, and will not change at 200-240℃. When the temperature rises to about 300℃, the molecular chain will break and degrade. Application: 1. Polyethylene glycol series products can be used as medicines; Polyethylene glycol with relatively low molecular weight can be used as solvent, cosolvent, O/W emulsifier and stabilizer to make cement suspension, emulsion and injection. Also used as water-soluble ointment matrix and suppository matrix. 2. The molecular weight of polyethylene glycol (PEG) used as cutting fluid in silicon wafer cutting is usually 300-400. This brand of PEG has suitable viscosity index, good fluidity, good dispersion stability to silicon carbide micropowder and strong sand carrying capacity. Oil-based oil-based cutting fluid has similar physical and chemical properties to polyethylene glycol-based water-based cutting fluid, good compatibility with silicon carbide micropowder, similar viscosity index to PEG300/400, and good sand carrying capacity. Compared with PEG300/400, oil-based cutting fluid has stronger chip removal ability, so when cutting silicon rods, the mortar prepared with oil-based cutting fluid can often cut silicon wafers with very good surface quality. For example, Japanese oil-based cutting fluid PS-LP-500D has a density of 0.826 g/cm3, a viscosity of about 96mmPa.s and a flash point of 1 12℃, and still has good fluidity at-10℃. Okay, Liaoning and Cologne also have oily cutting fluids, which are widely used in semiconductors.