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(a) annealing temperature
Annealing means providing an environment that makes the temperature of the silicon ingot in a slow speed, and is kept for a period of time. Annealing can eliminate the internal stress of silicon ingot, but also the existence of a long process of dislocation and other defects to give a certain degree of elimination, making the crystal is not easy to break. Even if the Long Jing is very smooth, the annealing will cause the failure of the ingot. For the next step is to conduct the ingot with slice, rupture is tantamount to waste. If only purified without ingot and a complete silicon ingot also prescribed rupture than ease of handling, such as going to the top and side skin. Therefore, the annealing process can not be ignored, because the long grain has been completed, to this time to the effect of processing.
After the completion of the long crystal, due to the high temperature of the top, therefore, the need to maintain the temperature slowly cooling. Usually, the power from the crystallization of the power in accordance with a very fixed rate decreased, at the same time, the thermal insulation body down, in the end, the power is also reduced to a minimum value.
Annealing temperature has different argument. Some heat preservation at 1300, which is the so-called high temperature annealing; some at 1100 C or so, called low-temperature annealing.
The best annealing temperature is controversial. Usually think should be completed long crystal, silicon ingot top and bottom temperature of intermediate values, this argument although seems to make sense, but would also like to think of silicon from cold temperature to annealing temperature, and from the hot temperature to annealing temperature and under heat stress is different. Cold temperature rise, thermal stress seems to be more, from this point of view, the annealing temperature should be around 1100 degrees celsius.
The annealing time according to the theory and experience, in the 3-4 hours, after the annealing temperature of 3 hours or so, after, you can carry out the natural cooling of the heating.
The so-called natural cooling stage to add heating stage, the first to make the silicon ingot in the heat of the internal heat of the slow cooling, and the heating body should also give a small amount of temperature, so that the temperature should not fall too fast. When temperature reaches 900, it can turn off the power, so that it can be completely natural cooling.
Is generally believed that temperature to 400 DEG C, can turn on the stove, and then to about 100 DEG C crucible even guard plate removed, but to put in airtight windless room and wait for more than 12 hours, in order to remove the support plate and the crucible.
(two) silicon ingot processing
When the ingot is removed from the furnace, the furnace plate and the bottom plate can be removed, and the retaining plate can be removed until the temperature is slowly cooled down, so that the temperature of the furnace can be removed, so that the ingot cracking can be caused by cooling. After removal of the retaining plate, the first of the silicon ingot production records.
Data record of silicon ingot
The following data are recorded for each silicon ingot:
Taking pictures, and to do to indicate direction and labeling the direction, for each silicon ingot furnace, in the furnace position (referring to the four ingot furnace furnace, furnace of a single spindle don't), production batch number and practice record name.
Measurement of silicon ingot size, including length of 12 sides and four sides of the central height;
Weight;
If the ingot has an abnormal, the abnormal phenomenon should be recorded. Such as the length and direction of the crack, the top of the case, the uplift of the area, size and direction; if possible, try to take pictures.
The data of silicon ingot is an important basis for the assessment of production quality. In addition, the data for the production process of silicon ingot analysis, quality improvement, process improvement has an important role, so it should be properly preserved.
Subsequent processing of silicon ingot
Before, after the completion of the silicon ingot casting machine directly to the root root. But now, due to the requirements of cost, each ingot manufacturers hope will evolution after the skin side feed and top leather recycled. The recovery of leather and leather top use needs to be cleaned, therefore, some work needs to be done in the square before.
First of all, the silicon ingot for sand blasting treatment, the six sides have to spray 1~5 mm thick. In particular, the top surface, to be sprayed with a thick. This is because the crucible on the surface of the silicon nitride coating, these coatings in the process of ingot casting part of silicon nitride powder will penetrate into the solidification of silicon ingot surface, therefore, to be removed. And the top surface of the silicon ingot, often shedding of the silicon nitride coating, and in the whole process of ingot, due to evaporation of the graphite heating body, so that part of the carbon in the silicon liquid surface, the formation of silicon carbide. Whether it is a silicon nitride or silicon carbide, the hardness ratio of silicon to a much higher, so that the formation of the silicon in the so-called "hard". Therefore, before the silicon ingot not prescribing by sand blasting on surface removal is to eliminate these hard points of a relatively simple way. Once after prescribing, the formation of edge leather, sandblasting process more trouble, and in addition may only use a grinding wheel. Through the blasted silicon ingot in roots, are less prone to break phenomenon.
If is metallurgical polycrystalline silicon or recycled materials, because impurities at the top may be thicker, the band will be removed the top of silicon ingot, resection of the thickness about at about 15 mm.
After sandblasting after silicon ingots can be sent to evolution machine. After prescribing, after cleaning, of small silicon ingot according to the measurements of the electrical resistivity values and minority carrier lifetime. According to the data of scribing and truncation. Silicon truncated after then grinding chamfering, to remove silicon surface damage layer formed in the square root.
After cleaning can be packaged, or sent to the workshop.
Cut down after the silicon material cleaning can be repeated use of ingot.
Edge of leather and leather top material after cleaning, can not be directly ingot or and the original raw material of admixture ingot, we must re melting purification, to ingot or with virgin polysilicon doped material ingot. This is due to

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