GUANGZHOU SUNPLUS TECHNOLOGY CO.,LTD , https://www.sunplussandpaper.com
During the entire cutting process, the main effects on the quality and yield of silicon wafers are the viscosity of the cutting fluid, the particle size and particle size of the silicon carbide powder, the viscosity of the mortar, the flow of the mortar, the speed of the steel wire, and the tension of the steel wire. And the workpiece feed rate.
First, the viscosity of the cutting fluid (PEG) Since the silicon carbide powder is suspended on the cutting fluid and cut through the steel wire during the entire cutting process, the cutting fluid mainly plays the role of suspension and cooling.
1. The viscosity of cutting fluid is an important guarantee for the suspension of silicon carbide powder. Due to the different system thinking of different machine development and design, the viscosity of the mortar is also different, that is, the viscosity of the cutting fluid is also different. Swiss wire cutters, for example, require cutting fluids with a viscosity of no less than 55, while NTC requires 22-25, and Ernst as low as 18. Only the viscosity of the cutting standard that meets the requirements of the machine can guarantee the uniform suspension distribution of the silicon carbide micropowder during the cutting process and the mortar can enter the cutting zone steadily through the mortar pipe with the steel wire.
2. Since the steel wire with mortar in the process of cutting the silicon material will undergo high temperature due to friction, the viscosity of the cutting fluid plays an important role in cooling. If the viscosity is not up to standard, the fluidity of the liquid will be poor, and the temperature can not be lowered to cause burns or breakage. Therefore, the viscosity of the cutting fluid ensures the temperature control of the entire process.
Second, the size and size of silicon carbide powder The cutting of solar wafers is in fact the steel wire with silicon carbide powder in the cut, so the particle size and particle size of the powder is the key to the smoothness and cutting ability of the silicon wafer. Granular rules, cut out of the silicon wafer will show a good finish; uniform particle size distribution will improve the cutting ability of the silicon wafer.
Third, the viscosity of the mortar Cutting machine for the strength of the cutting ability of silicon, and the viscosity of the mortar has an inseparable relationship. The viscosity of the mortar depends on the viscosity of the silicon cutting fluid, the suitability of the silicon cutting fluid and the silicon carbide powder, the proportion of the silicon cutting fluid and the silicon carbide powder, and the density of the mortar. Only the viscosity of the mortar that meets the requirements of the machine (such as NTC machine requirements about 250) can improve the cutting efficiency and improve the yield in the cutting process.
Fourth, the flow of mortar In the high-speed movement of steel wire, to complete the cutting of silicon material, the mortar must be pumped from the storage box to the sandblasting nozzle by the mortar pump, and then sprayed by the sandblasting nozzle to the steel wire. Whether the flow of the mortar is even or whether the flow can meet the cutting requirements plays a key role in cutting ability and cutting efficiency. If the flow rate cannot keep up, there will be a serious decline in cutting ability, resulting in line marks, broken lines, and even machine alarms.
Fifth, the speed of steel wire Because the wire cutting machine can carry on the unidirectional route and the two-way route according to the user's request, so the requirement for the line speed is different in two kinds of situations. In unidirectional routing, the steel wire always runs at a single speed (MB and HCT can be manually adjusted at different times depending on the cutting conditions), which is relatively easy to control. At present, the operation of one-way wiring is becoming less and less, and it is limited to MB and HCT machines.
In both directions, the speed of the steel wire starts to accelerate from the zero point in one direction to the specified speed in 2-3 seconds. After running for a period of time, it slowly decreases to zero in the original direction, and then pauses after 0.2 second at zero. Accelerate to the specified speed in the reverse direction, and then gradually reduce the cutting process to zero in the opposite direction. In the process of two-way cutting, the cutting ability of the wire cutting machine increases with the speed of the steel wire within a certain range, but cannot be lower than or exceeds the cutting ability of the mortar. If it is lower than the cutting ability of the mortar, there will be line marks or even broken lines; conversely, if the cutting ability of the mortar is exceeded, the slurry flow rate may not be able to keep up, resulting in thick flakes or even line marks.
At present, the average linear speed of MB can reach 13 meters/second, and NTC can reach 10.5 to 11 meters/second.
Six, steel wire tension Steel wire tension is one of the core elements of the silicon wafer cutting process. Poor tension control is an important cause of line marks, chipping, and even short lines.
1. If the tension of the steel wire is too small, the bending of the steel wire will increase, the sand-carrying capacity will decrease, and the cutting ability will decrease. As a result, line marks appear.
2, steel wire tension is too large, suspended in the steel wire silicon carbide powder will be difficult to enter the kerf, cut the cutting efficiency, line marks, etc., and the chance of breakage is very large.
3. If you cut the tape, sometimes it will cause the deviation from the zero point due to the long use time of the tension, such as the collapse of the edge.
The general tension control of wire cutting machines such as MB and NTC is less than one between the feed line and the take-up line. Only the difference between Ernst & Young's is 7.5.
7. Feed rate of the workpiece The feed rate of the workpiece is related to the speed of the steel wire, the cutting ability of the mortar, and the shape of the workpiece at different positions in the feed. The workpiece feed rate is determined by the above related factors during the entire cutting process, and it is also the least quantitative one. However, the control is not good, there may be adverse effects such as line marks, affecting the cutting quality and yield.
In short, the operation of the solar silicon wafer cutting machine is a fine job with more experience than technical processes and standards. Only in the actual operation, continuous summing up and discussion can be more than a smooth ride on the machine.
The linear cutting mechanism of solar wafers is that the machine guide wheel drives the steel wire during high-speed operation, so that the mortar mixed with polyethylene glycol and silicon carbide powder is sent to the cutting zone by the steel wire, in the high-speed operation and pressure online of the steel wire. The workpiece continuously rubs to complete the cutting process.