With the development of social economy, many single crystal silicon manufacturers are more skilled in the application of graphite thermal field, because there are two points: the front, the graphite felt insulation effect is good, the thickness reaches 100 mm, effectively guaranteeing the diameter The condition that the gradient temperature may be small, the second, the heat may be caused by the thickness of the graphite crucible reaching 250 mm, and the diameter of the upper and lower thermal insulation barrels may be large enough to have sufficient longitudinal heat dissipation function. It is well known that the problems in the use of graphite crucibles will lead to a reduction in the use time of graphite crucibles, which in turn will increase the cost for the manufacturers themselves. We believe in the special manufacture of graphite crucibles and thermal field processing parts. Talking about the common problems in the production of graphite hot field, how should we deal with it.
The components of the thermal field, such as heaters, three-rings, graphite holders, and heat shields, are all processed from graphite. In the production process, it is often possible to encounter the phenomenon of damage to the heating device. What is the cause of the damage of the graphite device, and what measures should be taken to extend the life of the graphite device? The damage of graphite devices is mainly caused by both human and degradation. As long as the human side strengthens management and strengthens employee awareness, it can lower losses to a lower point. The main discussion here is degradation. First, let's understand the characteristics of graphite. 1. High temperature resistance. The melting point of graphite is extremely high. It is 3850 degrees in vacuum and sublimated at low pressure. The sublimation temperature is 2200 degrees. Unlike general materials, graphite not only increases in temperature when temperature rises. Without softening, the strength is increased. At 2500 degrees, the tensile strength of graphite is doubled. 2. Special thermal shock resistance, the thermal expansion of graphite has anisotropy, so the macroscopic expansion coefficient is not large. In the case of sudden temperature changes, the volume change of graphite is not large, and its good thermal conductivity, Therefore, the thermal shock resistance of graphite is good. As stated in the above two points, the graphite member should be able to work stably at high temperatures for a long time.
Under normal circumstances, compared with other graphite devices such as heat shields and heaters, the flaps are the same material, the same manufacturer, and the same working environment. Why is the service life much lower than the heat shield and heater? The main reason for the fracture of the three-lobed crucible comes from the quartz crucible. 1. Since the density of the molten silicon is greater than that of the solid silicon, in the cooling process, the bottom material of the crucible will break through the quartz crucible, and the quartz crucible is attached to the three-lobed crucible. When the stress caused by the rupture of the quartz crucible is greater than the stress of the three-lobed crucible, the three-lobed crucible will break, which is why the remaining excess of the bottom material will break the three-lobed crucible. 2. If the heating time is too long, the quality of the quartz crucible is not enough, and the pH of the raw material does not meet the requirements, which will lead to silicon leakage and silicon infiltration. The molten silicon infiltrates into the gap between the three-lobed crucible and cools. It is to make the three-rings adhere to each other, and when they are cleaned, they may be broken due to separation. 3. In the heating process, only the heat source of the three-valve æ¥è‡ª comes from two aspects, one is the radiation of the heater, and the other is the conduction from the quartz crucible, which causes the three-lobed crucible to be heated unevenly, and expands in some directions when heated. , contracting in other directions, resulting in the fracture of the three-lobed ridge.
Daily maintenance method of graphite thermal field The thermal field is the core part of the vacuum resistance furnace, and its quality directly affects the performance of the furnace and its operating cost. The design of the thermal field is varied, and the specific design is chosen based on the specific analysis of the process. The thermal field of most vacuum resistance furnaces consists of four main components: the heater and its connecting parts, the thermal insulation component (or reflective screen), the thermal field support component, and the workpiece-carrying hearth. These accessories often need to be replaced regularly due to material problems or time of use. Under what conditions do graphite hot field fittings need to be replaced and which conditions need to be cleaned?
1. For the life expectancy to be replaced, in principle, it needs to be replaced (or let the experienced person identify it and decide whether to continue using it). For those who have not changed their life and are temporarily unused, seal them in a plastic bag, put them in a carton, and indicate the furnace number, number of furnaces, reason for replacement, source, date, and keep them in a safe place.
2. For partial damage (such as three flaps and one flap) and not reaching the end of life, it can be used or replaced (for the new three-valve åªæœ‰ with only a few furnaces, it is decided by the workshop supervisor to decide whether to use it or not. I can make up a set of pieces and use it for storage, but it can be stored for temporary use.) It is recommended to use on a purified furnace when re-use of the sealed storage.
3. Clean the thermal field oxides every time the furnace is dismantled, and clean the silicon infiltrated on the graphite parts. The diversion tube and the thermal insulation cover should be carefully cleaned to avoid accidents caused by foreign matter contamination. Take the graphite parts, in addition to pay attention to personal safety, also be careful to pay attention, pay attention to the safety of graphite parts.
4. Strictly follow the operating procedures to heat up, chemicalize, remelt, shut down the furnace, etc., to protect the graphite parts. After each furnace is dismantled, carefully clean the graphite fittings, carefully check the condition of the seed crystal and each graphite thermal field fitting, and make a detailed record.
5. Check the graphite fittings for cracks, especially graphite crucibles, graphite trays, and graphite masts. If there is a crack, report it to the workshop supervisor and replace it. Make a judgment or report to the workshop where there is silicon. the Lord. The squad leader is responsible for inspection and review before using the 5 furnaces before the expected service life. The workshop supervisor is responsible for inspection and review after using 5 furnaces before the expected service life.
6. After the service life of the graphite fittings expires, the graphite fittings (graphite tray, mast, graphite crucible) and other components that may cause significant loss after the overdue use are first removed and replaced with new ones, and the replaced graphite fittings are sealed for storage. The workshop, technical department and production department will be processed after the trial. Other accessories such as heaters, insulation tubes, and guide tubes should be inspected carefully to see if there are any micro cracks and defects. In principle, these graphite parts can continue to be used without the above defects. . Detailed records should be made for graphite hot field fittings that have a smoldering furnace.
7. Make detailed records of the graphite thermal field accessories in the event of an accident. For problematic graphite fittings, detailed records should be made and placed in designated locations to prevent confusion.
The above is the analysis of the common problems of graphite thermal field brought by Xinruida Graphite, which is specialized in the production of graphite crucible and graphite processing parts. If you want to know more news content of Xinruida Graphite, please visit Xinruida Graphite official website. , Xinruida Graphite will serve you wholeheartedly!
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