TWI481441B - Method and system for recovery of glycol solution from silicon sluury waste - Google Patents

Description

Method for recovering cutting fluid from muddy mud and recovery system thereof

The invention relates to a method for treating mud in a wafer cutting process, in particular to a method for recovering cutting liquid from mud and a recovery system thereof.

Press, wafer is a substrate material commonly used in the integrated circuit industry or the solar industry. Usually, after the growth of the ingot, the ingot is subjected to steps such as cutting, rounding, grinding and polishing to form a wafer for the integrated circuit industry or the solar industry.

At present, ingots are mostly cut by saw wires to form tantalum wafers; in order to reduce defects on the surface of tantalum wafers and the probability of wafer breakage, the ingots will reduce the mechanical properties of the cutting fluid during the cutting process. Damage caused by stress and thermal stress; in addition, the cutting liquid has good dispersibility for high-hardness tantalum carbide particles, which can further improve the yield of the ingot cutting process. In general, the cutting liquid for wafers mostly uses water-soluble glycols, and the polymer type cutting liquid is highly valued because of its stable nature, better lubrication and cooling effect, for example, polyethylene glycol (Polyethylene glycol) a copolymer of PEG), Ethylene oxide-Propylene oxide or a polyglycol solution such as a polyalkylene glycol (PAG).

At today's state of the art, it takes about 10 to 14 tons of cutting fluid per 1 MW of solar-grade tantalum wafer; and after cutting the ingot, a large amount of cutting fluid, The crushed niobium carbide particles, the cutting loss of the crucible and the saw wire metal and other materials will form a mud-like mud, which makes the wafer manufacturing industry have to face a large amount of mud to be treated, which not only pollutes the environment, takes up space, and wastes resources. It is even more contrary to the spirit of solar cells as a green energy source.

In fact, these polyglycol solutions are muddy in shape while mixing other solid particles, and their properties are still very stable and have a very high recovery value. As the demand for silicon wafers increases, the price of cutting fluids also As the climb climbs, manufacturers are scrambling to develop related recycling processes or methods to facilitate the recycling and reuse of cutting fluids. However, in the traditional method, most of the sludge is filtered several times to finally separate the cutting liquid and the solid particles; however, the viscosity of the mud is very high, and it is required to use a high-powered pumping pump, which is time-consuming and costly to handle. What's more, it will also cause damage to the filter.

In addition, the conventional method also first adds a stabilizer or a viscosity reducing agent to the mud, then separates the solid particles in the mud, and finally uses the distillation process to recover the cutting liquid; however, the high temperature of the distillation process not only makes the cutting liquid oxidatively deteriorate, In addition to the use of high-energy-consuming and expensive exhausting and decompressing devices, there are problems such as slow removal rate of the viscosity reducing agent and difficulty in controlling the moisture content of the cutting fluid after recovery. In addition, the conventional method also initially separates the liquid mixture in the mud, and then uses the heating method to recover the cutting liquid; similarly, this recovery method requires the use of a high-energy heating device.

Therefore, how to reduce the manufacturing cost of the germanium wafer and reduce the pollution caused by the muddy mud, and how to obtain the cutting fluid, the crucible and the tantalum carbide which can be recycled and reused from the mud, is a desire of those skilled in the art to achieve The goal.

The main object of the present invention is to provide a method for recovering cutting liquid from a pure mud with low pollution, low energy consumption, simple and rapid process, and high recovery rate, and a recovery system thereof, thereby reducing the manufacturing cost of the silicon wafer and reducing the defect. The environmental impact of wafer cutting waste.

For the purposes described above, the present invention provides a recovery cut from the mud The liquid method comprises the following steps: first, diluting a slurry of a wafer cutting process into a mixed solution, the mixed solution having a first solid content; and then performing solid-liquid separation on the mixed solution to obtain a liquid state a mixture and a solid mixture, wherein the liquid mixture has a second solid content; thereafter, an electrolyte is added to the liquid mixture, and after a predetermined period of time, the liquid mixture is separated into an immiscible cutting liquid phase and an aqueous phase. And finally, the cutting liquid is taken out.

In an embodiment of the invention, the electrolyte is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, potassium sulfate or a group thereof.

In an embodiment of the invention, the electrolyte is added at a concentration of at least greater than 0.5 M.

In an embodiment of the invention, the first solid content is between 10 and 15 wt%, and the second solid content is less than 5 g/L.

In an embodiment of the present invention, after the step of taking out the cutting liquid, further comprising performing a vacuum distillation process.

In an embodiment of the invention, the predetermined time is 10 to 30 minutes.

In one embodiment of the present invention, the mixed solution is subjected to solid-liquid separation by a centrifugal separation method, a pressure filtration separation method, a sedimentation separation method, a membrane filtration method, or a decantation analysis method.

The present invention further provides a recovery system for recovering a cutting fluid from the mashed mud described above, comprising a stirring tank, a solid-liquid separator and a phase separation tank, wherein the solid-liquid separator is connected to the a stirring tank for accommodating a liquid mixture, and adding an electrolyte to separate the liquid mixture into a cutting liquid phase and an aqueous phase, and the phase separation tank is connected to the solid-liquid separator.

In an embodiment of the present invention, a vacuum distillation apparatus is further included, and the vacuum distillation apparatus is connected to the phase separation tank to reduce the moisture content of the cutting liquid phase.

In an embodiment of the present invention, a fine filtration unit is further included, and the fine filtration unit is connected to the solid-liquid separator, and is suitable for sorting large-sized particles and small-sized particles in the solid mixture. .

The present invention has at least the following advantages: the recovery of the cutting fluid from the pure mud of the present invention By adding an electrolyte to the liquid mixture, it is only necessary to stand for 10 to 30 minutes to separate a large amount of water to completely recover the polyglycol cutting solution and reuse it. The overall process is simple and fast, low pollution and high recovery rate. . Moreover, all the steps in the method of the present invention do not require the use of high energy consuming and expensive equipment such as pumping, distillation and heating, which can greatly reduce the energy consumption and manufacturing cost of the wafer.

The above description of the present invention and the following description of the embodiments are intended to illustrate and explain the principles of the invention, and further explanation of the scope of the invention.

10‧‧‧Stirring tank

20‧‧‧ solid-liquid separator

30‧‧‧ fine filter unit

40‧‧‧phase separation slot

50‧‧‧Reduced distillation unit

S12 to S18‧‧‧ process steps

Figure 1 is a block diagram of a recycling system of the present invention.

2 is a flow chart of a method for recovering a cutting fluid from a muddy mud of the present invention.

The invention mainly discloses a method for recovering a cutting liquid from a muddy mud and a recycling system, which can recover and reuse the cutting liquid in the mud of the wafer cutting process, wherein the "muddy mud" comprises two parts of a liquid and a solid. Wherein, the liquid portion is a polyglycol-based cutting liquid, such as polyethylene glycol (PEG), ethylene oxide (Ethylene oxide)-propylene oxide (Propylene oxide) copolymer or polyolefin based Polyalkylene glycol (PAG); the solid part includes abrasive particles (such as niobium carbide particles), lost polycrystalline germanium or single crystal germanium particles and saw wire metal. In the embodiment, the solid content in the mud is about 700 g/L.

Please refer to FIG. 1 , which is a flow chart of a method for recovering cutting fluid from muddy mud according to a preferred embodiment of the present invention. The method of this embodiment includes a dilution step S12, a solid-liquid separation step S14, and an electrolyte addition phase separation step S16. In the following, the details of each step will be described in detail with reference to the schematic diagram of the recycling system shown in FIG. 2, and those skilled in the art can easily understand the advantages and effects of the present invention by the contents of the disclosure, without departing from the invention. Various modifications and changes are made in the spirit to perform or apply the present invention. method.

First, the diluting step S12 is performed to dilute the mud of a wafer cutting process into a mixed solution, and the mixed solution has a first solid content. Specifically, since the viscosity of the mud is very high, in order to reduce the viscosity to increase the efficiency of the subsequent solid-liquid separation, in the present embodiment, the mud is placed in a stirring tank 10, and the diluent is continuously added and stirred until the mud is muddy. The viscosity is reduced to a certain extent to form a mixed solution with a low viscosity.

It is to be noted that the diluent used in the present embodiment is mainly water, but is not limited thereto. In addition, the amount of water used for dilution in this step must be able to adjust the first solid content of the mixed solution to between 10 and 15 wt%, taking into account both the efficiency of solid-liquid separation and the process speed. For example, the lower the first solid content of the mixed solution, the better the solid-liquid separation efficiency, but due to the volume limitation of the stirring tank 10, the obtained mixed solution having the first solid content is less, so that the cut to be recovered is obtained. The larger the amount of liquid, the more frequently the dilution step S12 is performed, affecting the overall process rate.

Next, a solid-liquid separation step S14 is performed, and the mixed solution is subjected to solid-liquid separation to obtain a liquid mixture and a solid mixture, wherein the liquid mixture has a second solid content. Specifically, the mixed solution obtained in the step S12 can be subjected to solid-liquid separation of the low-viscosity mixed solution by means of centrifugation, pressure filtration separation, sedimentation separation, membrane filtration or decantation analysis; in the present embodiment, The solid-liquid separator 20 separates the solid (solid mixture) and the liquid (liquid mixture) in the sludge by centrifugal separation, but is not limited thereto. Wherein the second solid content of the liquid mixture is at least less than 5 g/L, the cutting liquid to be recovered in the present invention is present in the liquid mixture separated in this step.

Further, the solid mixture separated from step S14 (including niobium carbide, niobium and sawing metal such as iron, etc.) may be additionally sorted via the fine filtration unit 30 to further sort out economical value of niobium carbide. The fine filtration unit 30 is, for example, a water cyclone, which is a difference in the fineness characteristics such as the size and density of each particle in the mixture, so that the mixture is subjected to different operations in the cavity of the water cyclone separator. Force, such as: centrifugal force, centripetal buoyancy, fluid drag, etc., to produce a separation effect.

Wherein, the mixture to be separated is introduced into the cavity from the inlet of the water cyclone, and after the mixture to be separated is subjected to high-speed and tangential centrifugal sedimentation, the large particles are smashed into the hydrocyclone. The wall of the chamber slides along the wall of the hydrocyclone and is discharged from the bottom outlet of the hydrocyclone; while the small particles are pumped upwards and discharged from the overflow of the hydrocyclone to achieve separation. Effect.

Thereafter, an electrolyte addition phase separation step S16 is performed to add an electrolyte to the liquid mixture, and after a predetermined period of time, the liquid mixture is separated into an immiscible cutting liquid phase and an aqueous phase. In this embodiment, the liquid mixture (including water and polyglycol cutting liquid) separated by step S14 is placed in a phase separation tank 40, and the added electrolyte may be selected from sodium hydroxide, potassium hydroxide and chlorine. One of the group consisting of sodium, potassium chloride, potassium sulfate or the above compounds, and the concentration is required to be at least greater than 0.5 M to achieve a better phase separation effect. It is added that when an acid electrolyte such as hydrochloric acid, sulfuric acid, nitric acid or a combination thereof is added, the phase separation function cannot be achieved because it can participate in the reaction of the polyhydric alcohol.

According to this, a distinct phase separation interface (the interface between the polyglycol-based cutting solution and water) can be observed after standing for 10 minutes. The longer the standing time, the more obvious the phase separation interface is to be allowed to stand for 30 minutes. The polyglycol-based cutting fluid can then be completely recovered. The principle is that the electrolyte breaks the hydrogen bond between the polyglycol-cutting solution and the water, so that the solubility of the polyglycol-based cutting solution in water is lowered, and then the phase separation occurs.

In a variant embodiment, after the polyglycol-based cutting liquid is taken out, a vacuum distillation step S18 may be further performed, and the vacuum distillation apparatus 50 is used to remove trace water contained in the polyglycol-based cutting liquid (about 1~). 5 wt%) to improve the quality of the recovered polyglycol cutting fluid.

In order to complete all the steps in the method for recovering the cutting liquid from the mud, the present invention further provides a recovery system comprising a stirring tank 10, a solid-liquid separator 20, a fine filtering unit 30, a phase separation tank 40 and a Vacuum distillation unit 50. Among them, solid-liquid separator 20 is connected to the agitation tank 10, and the fine filtration unit 30 is connected to the solid-liquid separator 20, and is suitable for sorting large-sized particles and small-sized particles in a solid mixture, and the phase separation tank 40 is also connected to the solid-liquid separator. 20. The vacuum distillation apparatus 50 is connected to the phase separation tank 40 to further reduce the moisture content of the polyglycol-based cutting liquid.

In summary, the present invention has at least the following advantages over conventional recycling methods:

1. The method for recovering the cutting liquid from the mud in the present invention by adding an electrolyte to the liquid mixture, and only needs to stand for 10 to 30 minutes to separate a large amount of water to completely recover the polydiol cutting liquid and reuse it. The overall process is simple and fast, low in pollution, low in water content and high in recovery rate.

2. Furthermore, all steps in the method of the present invention do not require the use of energy-intensive and expensive equipment such as pumping, distillation, and heating, which can reduce energy consumption and greatly reduce the manufacturing cost of the wafer.

3. In addition, the method of the present invention does not cause an increase in the acid value during the process of recovering the polyglycol-based cutting liquid, and thus the stability of the recovered cutting liquid is high.

The invention has already met the requirements of the invention patent and submitted an application according to law. However, the above disclosure is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and thus the equivalent changes or modifications made in the scope of the present application are still covered by the present application.

S12 to S18‧‧‧ process steps

Claims (10)

A method for recovering a cutting liquid from a muddy mud, comprising the steps of: diluting a mud of a wafer cutting process into a mixed solution, the mixed solution having a first solid content; and performing solid-liquid separation on the mixed solution, Obtaining a liquid mixture and a solid mixture, wherein the liquid mixture has a second solid content; adding an electrolyte to the liquid mixture, after a predetermined time, the liquid mixture is separated into an immiscible cutting liquid phase and An aqueous phase; and removing the cutting fluid. A method of recovering a cutting solution from a slurry according to claim 1, wherein the electrolyte is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, potassium sulfate or a group thereof. A method of recovering a cutting solution from a slurry according to claim 1, wherein the electrolyte is added at a concentration of at least 0.5 M. A method of recovering a cutting solution from a slurry according to claim 1, wherein the first solid content is between 10 and 15% by weight and the second solid content is less than 5 g/L. A method of recovering a cutting fluid from a slurry according to claim 1, wherein after the step of removing the cutting liquid, further comprising performing a vacuum distillation process. A method of recovering a cutting liquid from a pure mud as described in claim 1, wherein the predetermined time is 10 to 30 minutes. A method for recovering a cutting liquid from a pure mud according to claim 1, wherein the mixed solution is subjected to solid-liquid separation by a centrifugal separation method, a pressure filtration separation method, a sedimentation separation method, a membrane filtration method or a decantation analysis method. A recovery system using the method for recovering a cutting fluid from the mud according to claim 1, comprising: a stirring tank; a solid-liquid separator connected to the stirring tank; and a phase separation tank In the solid-liquid separator for accommodating a liquid mixture And adding an electrolyte to separate the liquid mixture into a cutting liquid phase and an aqueous phase. The recovery system of claim 8, further comprising a vacuum distillation unit coupled to the phase separation tank for reducing the moisture content of the cutting liquid phase. The recovery system of claim 9, further comprising a fine filtration unit coupled to the solid-liquid separator, adapted to sort large-sized particles and small particle diameters in the solid mixture Particles.