FR2553297A1 - LIQUID FILTER, IN PARTICULAR FOR CONTINUOUS REMOVAL OF PARTICLES CONTAINED IN WATER AFTER CUTTING OF SEMICONDUCTOR DEVICES - Google Patents

Abstract

LIQUID FILTER INCLUDING: A WATERPROOF CONTAINER 10 INCLUDING AN INLET 10A FOR RECEIVING WATER TO BE FILTERED AND AN OUTLET 10B FOR DRAINING THE FILTERED WATER; AND -A FILTERING MEANS 1 PROVIDED IN THE CONTAINER TO CUT A FLOW OF WATER CAUSED FROM THE INLET TO THE OUTLET, SO THAT A FLOW OF NON-FILTERED WATER IN BYPASS IS CAPTURED BY THE FILTERING MEANS, CHARACTERIZED IN WHAT THE FILTER MEDIA 1 IS WOUND INTO A FILTER DRUM 5 CONSTITUTES A NUMBER OF FILTER LAYERS AND AT THE CENTER OF WHICH A CAVITY 5A IS FORMED, AND IN THAT ONE END OF THE FILTER MEDIUM 1 IS WOUND ON A COIL WRAPPING 6 PROVIDED IN SEALED CONTAINER 10 SEPARATE FROM THE FILTER DRUM TO RETAIN AUXILIARY FILTER LAYERS FROM THE FILTER MEDIA.

Description

The present invention relates to a small liquid filter which

  allows effective and continuous removal of particles from a liquid over a long

period of time.

  In the manufacture of semiconductor devices such as Large Scale Integration (LSI) devices, a rod-shaped semiconductor element is cut into a number of disk-shaped substrates, and semiconductor circuit elements. 10 are respectively formed into a number of small rectangular surfaces defined thereon, after which the substrates are each cut into individual semiconductor devices. The cutting operation takes place while water is sprayed onto the As a result of this, the water used for cutting contains large amounts of cutting chips with a diameter of between 0.3 and 1 g of semiconductor material, and the water further contains substances toxic when the semiconductor substrates 20 are made of materials such as gallium arsenide; so the wastewater can not be

directly evacuated.

  A known solution to this problem is to treat the wastewater by a coagulant precipitation process, but this process leads to insufficient treatment. Instead of the above process is used today a process which uses a resistant filter paper to water which is easy to handle and capable of removing fine particles with a diameter of less than 0.3, as a result of a remarkable improvement in its filtration capacity. cartridge in which, for example, an embossed paper filter paper means (hereinafter referred to as filter paper) is supported in circular form in a box, and the water to be treated is fed to the filter paper, for example from A further example is a method in which a portion of a wound filter paper is disposed to extend across a pass. water and, when the cutting chips are deposited on the part

  overflowing, the filter paper is taken up on a roll.

  These methods are easy to implement and offer an excellent filtration quality compared to the coagulant precipitation method used hitherto. However, in these processes, the lowering of the filtration performance is inevitable. this being due to the low-thickness of the filter paper used; in fact, among all the cutting chips captured on the surface of the paper, some of the chips of a diameter smaller than that of the pores of the filter paper are inevitably forced through the filter paper, by the pressure of the water, towards the surface. Thus, the processes mentioned above have the common disadvantage that the desired filtration quality can not be achieved. Furthermore, in the first process, ie the cartridge system, the filter paper is embossed. in order to increase the filtration volume, but the filtration volume obtained remains low, which requires frequent exchange of the cartridge This not only prevents long-term filtration continuously, but also involves cartridge exchange operations difficult, this

  which leads to an increase in manufacturing costs for semiconductor devices.

  An object of the present invention is to create a small liquid filter which does not exhibit the aforementioned defects of the methods of the art

  and capable of performing a continuous filtration operation for a long period of time

  serving a high filtration quality.

  According to the invention, the liquid filter is characterized by an arrangement such as a filtering means wound in a filtering drum at the center of which is formed a cavity, is wound on a winding coil disposed in the cavity, a filter layer auxiliary being kept outside the filtering drum and the water to be treated being fed into the filtering drum

  from the inner peripheral surface thereof for filtration.

  The winding spool may be placed outside the cavity. In this case, the auxiliary filter layer is kept inside the filtering drum and the water to be treated is fed into the filter drum 15 outer periphery to be filtered. Various other features of the invention

  come out from the detailed description which

  follows. Embodiments of the subject of the invention are represented, by way of non-limiting examples,

in the attached drawing.

  Figs. 1A, 1B and 2 are plan views for explaining the principles of the present invention.

  Figs. 3A and 3B are partial cross-sectional front views illustrating an embodiment of the present invention, the second being a sectional view according to

line A-A 'of the first.

  Fig. 4 is a diagram of the process of operation.

  Fig. 5 is a perspective view illustrating another example of a filter drum used in the embodiment shown in Fig. 3. Fig. 6 is a partial sectional front view showing another embodiment of the present invention. invention. Fig. 7 is a perspective view illustrating another example of a filter drum used in the

  embodiment shown in FIG. 6.

  The characteristic of the present invention is as follows: according to the present invention, the filter paper 1 is wound into a multilayer filtering drum 5 at the center of which is formed a cavity 5a, as shown in the plan views of FIGS. 1 B, 10 and the water to be treated is conveyed through the filter drum from its inner peripheral surface to its outer peripheral surface, as indicated by FIG.

  arrow A 1 and, simultaneously, a winding spool 6, to which one end of the filter paper is attached, is disposed in the cavity 5a of the filtering drum 5.

  The inner diameter of the filter drum 5 and the outside diameter of the winding spool 6 are chosen so that a space for the admission of the water to be treated is permanently defined between the filter drum 5 and the winding spool 6 on which the filter paper 1 is wound, in order to allow the filtration of the water passing through the filtering drum from the inside to the outside of the filter drum whenever the pressure of the filter As the water increases due to the deposition of cutting chips 4 on the inner peripheral surface of the filter drum, the innermost layer of filter paper I on which the chips are deposited is wound on the winding spool. 6

  layer after layer, while an auxiliary filter layer F remains in place.

  In the example shown in FIG. 1A, a rotary winding spool 6 is disposed in the center of the cavity 5a of the fixed filtering drum 5 and, in order to keep under tension the filter paper wound on the filtering drum 5 during the winding of the filter paper on the winding spool 6.1 a feed position of the filter paper is subjected to the action of an urging member 8 which is arranged to exert a pressure force necessary for the With the aid of a spring 7 In the example shown in FIG. 1B, the winding spool 6 is urged by a spring 9 against the inner peripheral surface of the filtering drum 5 to rotate it, the filter paper 1 being thus wound on the winding spool 6 without loosening the winding of the filter paper on the filtering drum 5, thanks to

  the use of friction between the inner peripheral surface of the filter drum 5 and the winding spool 6.

  During filtration using the filtering drum 5 on which the filter paper 1 is wound in layers as proposed by the present invention, the chips 4 which have passed through a first layer of filter paper without being captured by it are deposited on the surface of a second layer of filter paper, and the chips 4 which still pass through the second layer are captured by a third layer Subsequently, the smallest chips 4 are deposited layer by layer in the manner described. Thus, by appropriate selection of the number of layers of the auxiliary filtering F, it is possible to carry out the filtration of the wastewater by substantially completely preventing the cutting chips 4 from flowing towards the outlet. In addition, according to the present invention, since the filter paper is wound into a multi-layer filter drum, the common defects of the above-mentioned conventional processes are overcome. The total area of the filter paper can be significantly increased compared with the case of the cartridge system. This considerably lengthens the filtration time continuously, and therefore significantly reduces the time and operations required for the exchange of the filter paper. the cartridge system, when a filter paper 5 m long and 0.5 m wide is wound to have an outer diameter of 0.5 m, the surface of the filter paper is 2 In contrast to this, according to the present invention, when a filter paper of the same dimensions is wound in 1000 layers with an average diameter of 0.3 m, the total area is about 471 m 2, ie In addition, because the filter paper is generally about 0.2 mm thick, the total thickness of the filter paper layers, even when wound in 1, is about 188 times greater than that of the cartridge system. 000 layers, is 0.2 m so the outside diameter of the roll, which is equal to the sum of the average diameter above and this thickness, is substantially equal to the outside diameter in the case of the cartridge system, and the filter drum can be

  housed in a container having substantially the same diameter.

  According to the present invention, because the filter paper 20 is wound on a winding spool in the filter drum, the outer diameter of the filter drum is always constant, which is advantageous.

  in that the filter can be given small dimensions.

  An exemplary embodiment of the present invention is described below. Fig. 3A is a partial sectional view illustrating an embodiment of the present invention, and Fig. 3B is a sectional view of Fig. 3A along line AA '. In FIGS. 3A and 3B, the reference numeral 10 designates a sealed container, has a wastewater inlet, 10b a clean water outlet and 10c a cover for replacing the filtering drum, fixed by bolts and The reference numeral 5 designates the filter drum in which the filter paper is wound, the cavity 5a being formed at the center thereof. In addition, adhesive layers 5b are formed on the upper and lower end faces. of the filter drum and have a thickness such that they do not hinder the winding of the filter paper, so that the water to be treated is admitted into the filter drum 5 only from its inner peripheral surface Reference 11 designates a punched cylindrical metal plate having a number of perforations which is sealed at its upper and lower ends, by welding, to the inner wall of the sealed container 10 Reference numeral 12 denotes an annular lower support plate whose outer peripheral portion is sealingly connected to the lower end of the punched metal plate 11, and 13 is an annular upper support plate which is removably and sealingly screwed to the punched metal plate 11. seal 5 c joined to the outer peripheral surface of each of the upper and lower ends is inserted into the punched metal plate 11, after which the upper support plate 13 is screwed onto the upper edge portion of the metal plate. punched 11 to take in sandw ich the filtering drum 5 between the upper support plate 13 and the lower sup-port plate 12, so as to support the filtering drum 5 so that the water to be treated does not flow towards the outlet of purified water through the interstices between the support plates 12 and 13 and the filtering drum 5 by the punched metal plate 11 The reference 6 represents the winding spool, and 14

  an upper support disc, which is attached to the lid 10c.

  The reference 15 designates a sealed lower bearing, and the winding spool 6 is driven by a motor 16 by a reduction gear 17 The reference 8 designates the pressing member and 18, 19 denotes an upper support and a lower support for the pressing member, which are respectively fixed on the upper part and on the lower part of the winding spool 6 As shown in FIG. 3B, the pressing member 8 is movably supported by the upper and lower supports 18 and 19 inserted in the support holes 8a and 8b formed in the upper and lower ends of the pressing member 8 The pressing member 8 is pushed by the spring 7 so as to move outwardly, 10 during the winding of the filter paper in oblong holes 12a and 13a formed radially in the support plates 12 and 13, and is constantly urged against the inner peripheral surface of the filtering drum 5 In order to define the winding position of the filter paper 1 wound in the filter drum 5 to become loose. In addition, the fine wastewater from the inlet 10a is filtered by flowing through the filter drum 5. its inner peripheral surface towards its outer peripheral surface, as indicated by the arrows, and the purified water is discharged through the outlet

  b crossing the punched metal plate 11.

  The reference 20 designates a pressure sensor, and an electronic switch. The pressure sensor 20 detects a pressure increase on the side of the waste water inlet 25 of the filter drum 5 and, when the pressure reaches, for example, a value of 2 to 3 kg / cm 2, indicated by P1 on the diagram of the process of operation shown in FIG. 4, the pressure sensor 20 produces a signal for turning on the electronic switch 30 21, thereby driving the motor 16 and wind the filter paper 1 on the winding spool 6 When the portion of the filter paper on which are deposited cutting chips 4 is thus wound, and that the pressure returns to its initial value, indicated in P 2 in FIG. 4, the pressure sensor 20 stops producing the signal, to interrupt the winding of the filter paper 1 on the winding spool with the aid of the motor 16. Then, the above operations are repeated each time the reference point 22 designates a control switch of the winding, for example a magnetic switch with blades, whose connecting cable exits without passing water from the sealed container 10 Reference 22a designates its actuator and 23 a signal generator, which is mounted at the lower end of the pressing member 8 When the thickness of the filtering drum 5 reaches a certain value as a result of the winding of the filter paper 1 on the winding spool, the electronic switch 21 is blocked to inhibit any subsequent winding of the filter paper by the motor 16, to ensure that the paper layer auxiliary filter F remains thick enough to prevent the cutting chips 4 from the trab pour pour to the outlet side Thus, if we continue the filtration, then the cutting chips 4 is The reference 24 designates a timer, an inverting solenoid valve and another liquid filter of the present invention. The timer 24 produces an output when the pressure sensor 20 continuously detects, for a certain period of time, a pressure at the point P 3 in FIG. 4, for example a pressure exceeding 2 to 3 kg / cm 2, in the situation in which the cutting chips 4 are deposited more and more. , as mentioned above As a result, the inverting solenoid valve 25 is switched on the path

  of the liquid filter 26, to continue the filtration.

  Reference 27 designates an inlet for wastewater from a cutting unit. Tests have shown that the filter of the present embodiment delivers filtered water having a high degree of cleanliness, and that it allows continuous processing. long term

for the treatment of wastewater.

  For example, when wastewater from a cutting unit, which contained about 30,000 to 50,000 cutting chips per 10 cm 3, was filtered at a flow rate of 25 liters / minute, the number of chips contained in the filtered water was between 100 and 300 per 10 cm 3, and the size of the discharged particles was between 0.3 and 1 A.

  Filtering quality has not changed significantly, even after continuous operation for 500 hours.

  In addition, each semi-conductor cutting unit typically requires water (industrial or pure) at a rate of 25 liters / minute, and it is quite

  current that 30 cutting units of an installation operate at full speed for 24 consecutive hours.

  Thus, the amount of water required for each cutting unit for 30 days is 25 x 60 x 24 x 30 = 1080 tonnes, that is, the amount of water consumed can reach 1080 x 30 tonnes per day. However, with the present invention, the filtration is very efficient and does not use any chemical, and thus allows the reuse of the filtered water,

  to ensure a sensible water saving.

  Although, in the foregoing, the present invention has been described as being applied to the filtering of wastewater from cutting units in the manufacture of semiconductor devices, it will be understood that the invention also applies to the treatment of other waste waters, for example in nuclear power plants and, in this case, the filter quality of the filter paper used is determined according to the particle size of the wastewater In addition, although, 1 1 in the above embodiment, the winding of the filter paper on the winding spool is interrupted to leave the auxiliary filter layer F on the evacuation side, it is also possible to prepare the filter layer auxiliary F separately from the filter drum 5 and assemble it to the filter drum 5 outside thereof, so that the filter paper of the filter drum is fed to the layer This solution makes it possible to dispense with devices for leaving the auxiliary filtering layer F, such as the magnetic reed switch 23, etc., and

  thus allows a simplification of the filter.

  Although, in the foregoing, paper-like wire means is wound in the filter drum, it is also possible to wind in the filter drum 5 a wire, for example a long wire of an outer diameter. from 3 to 8 mm, formed by joining fibers of 2 to 20 A, so that a wire 28 forming a layer and a wire 28b forming the next layer intersect, as seen in perspective at the 5, and the wire 28 is wound on the winding coil 6 each time cutting chips are deposited In this case, the filtering function is performed by air gaps between the adjacent wires and by air gaps between the fibers forming the wire Thus, a required filtration quality can be achieved by appropriate selection

  how to wind the wire, the spacing of the wires and the type of wire used.

  Another embodiment of the present invention is described below. The feature of this embodiment is as follows: The filter paper is wound into a multilayer filtering drum 35 at the center of which a cavity 5a is formed, as shown in FIG. plan view of Fig 2, and the water to be treated is conveyed through the filter drum from its outer peripheral surface to the cavity 5a, as indicated by the arrows; in addition, a rolling coil 6, on which is fixed one end of the filter paper 1, is disposed outside the filtering drum 5 whenever the pressure of the water passing through the filtering drum increases. due to the deposition of cutting chips 4 on the outer peripheral surface of the filter drum during filtration, the outermost filter paper layer on which the chips are deposited is wound on the reel winding 6; in this case, however, no auxiliary filter layer F is wound on the winding spool 6 When filtering wastewater by passing it through the filter drum 5 from its outer peripheral surface to its inner peripheral surface, even if a portion of the cutting chips 4 deposited on the outer peripheral surface passes through the first layer under the effect of water pressure, they will be captured by the next layer, the second, and even if they are still forced to cross, they will eventually be captured by a third or fourth layer, or an even further layer therein, using an auxiliary filter layer F having a number of layers such as it prevents the smaller chips from crossing it to the inner peripheral surface of the filter drum, and by winding the filter paper every time a predicted pressure increase appears determined by the deposition of cutting chips 4, it is possible to prevent almost completely the chips to go out to the evacuation Thus the common defects in the processes

  In addition, according to the present invention, the total area of the filter paper may be

  increased compared to the usual cartridge system.

  This substantially increases the filtration time continuously, and therefore greatly reduces the time and the operations necessary for the exchange of the filter. For example, in the cartridge system, when a filter paper having a length of 5 m and a width of 0.5 m is wound so as to have an outside diameter of 0.5 m, the surface of the filter paper is 2.5 m 2, depending on the present invention, when a filter paper of the same dimensions is wound in 1000 layers with a mean diameter of 0.3 m, the total area is about 471 m 2, about 188 times more than in the case of the cartridge system Fig 6 is a cross-sectional view Fig. 6 shows a container, an inlet for the water to be treated and a hood, which is mounted with bolts and nuts on the container 10 so as to be detached therefrom for replacement of the filter drum 38 is a rotating cylinder which is closed at its upper end but has a clean water outlet. b) 38a designates a number of clean water discharge ports over the entire peripheral surface of the cylinder 38; 2 '38 b denotes a disc-shaped lower support flange fixed to the outer peripheral surface of the cylinder 38 at the lower end portion thereof; and 38c denotes an upper support flange demountably screwed to the top of the rotary cylinder 38. The reference numeral 5 denotes the filtering drum, in which the filter paper 1 is wound in layers so that the filtering drum comprises at its center a cavity 5a of a diameter slightly greater than the outside diameter of the rotary cylinder 38 A water seal 39a is placed on the lower support flange 38b and the rotary cylinder 38 is received in the cavity of the filter drum, after which another water seal 39b is placed on the filter drum, then the upper support flange 38c is fixed with screws to the rotary cylinder 38 so as to the water to be treated flows from the inner peripheral surface of the filter drum to its peripheral surface

  The reference numeral 40 designates a sealed bearing.

  to water and 41 designates a support plate which is fixed to the container 10 so that it can be separated therefrom with the hood 10c, and which rotatably supports the rotary cylinder 38 by the upper and lower parts its axis in combination with the sealing bearing 40 The water to be treated, which is fed into the content 10 through the inlet 10a, passes through the filter drum 5 from its outer peripheral surface to its inner peripheral surface, and flows through the discharge ports 38a of the rotary cylinder 38, for

  then be evacuated by the output l Ob located at its lower extremity.

  The reference 6 designates a winding spool, which is rotatably supported by the support plate 41 and by a water-tight bearing 43 provided at the lower end of the container. The reference 16 designates a motor provided with a reduction gear, which is coupled to the end portion of a shaft protruding from the container 10 to drive the take-up spool 6, to wind therein the filter paper 1 from the outer periphery of the spool of the spool. filter 5 The reference 20 designates a pressure sensor, and 21 an electronic switch The pressure sensor 20 detects the pressure in the container 10 at the level where the water to be treated flows into the filter drum 5, and when the pressure reaches for example a value

  from 2 to 3 kg / cm 2, for which filtration can not

255329?

  continue, as indicated in P1 on the diagram of the process of operation shown in FIG. 4, the pressure sensor 20 produces a signal, by which the electronic switch 21 is turned on to connect an AC power source to the motor 16, to drive the winding spool 6 to wind the filter paper 1 When the outermost layer of filter paper, on which are deposited the cutting chips 4, is wound, and that As a result, the pressure returns to its initial value, indicated in P 2 in FIG. 4, the pressure sensor 20 ceases to produce the signal, to stop the motor. Thereafter, each time the increase in pressure appears, the above operations are repeated, to expose the next layer of filter paper 1 to the deposition on it of the cutting chips. The reference 47 denotes a tight winding position control switch and a signal generator The switch 47 is arranged between the filter layers 5b to be wound up 20 and the auxiliary filter layer F of the filtering drum 5 When the innermost winding filter layer is wound up to reveal the filtering layer auxiliary F, the switch blocks the transmission of a signal by the signal generator 23, 25 which controls the electronic switch 21 to cut off the AC power, to prevent the start of the motor 16 and to inhibit any subsequent winding of the filter paper, even if, subsequently, the electronic switch 21 is made passing through the pressure sensor 20 The reference 24 designates a timer, and 26 another liquid filter apparatus. Timer 24 produces a signal when it detects continuously for a certain time that the pressure sensor 20 detects a pressure value of greater than 2 to 3 kg / cm 2, as indicated at P 3 in FIG. 4, which corresponds to a situation in which the cutting chips 4 are deposited more and more as a result of the abovementioned inhibition of any subsequent winding of the filter paper. Then a solenoid valve 25 is tilted on the path of the liquid filter 26, for

  continue filtration Reference 27a designates an inlet for wastewater from a cutting unit.

  It turned out that the above facility was delivering

  filtered water with a high degree of cleanliness and a long-lasting continuous water treatment.

  A filter apparatus can be made whereby, when wastewater from a cutting unit containing about 30,000 to 50,000 cutting chips per 10 cc is filtered at a flow rate of 25 liters / minute. , the number of chips contained in the filtered water are reduced from 100 to 300 (with a particle size of 0.3 to 1 A) per 10 cm 3 In addition, it was found that it was possible to achieve equipment capable of performing continuous filtration for more than 500 hours, and at the same time the filtered water could be reused for cutting, because of its high degree of cleanliness and the fact that no chemical This is why the present invention provides a remarkable water conservation for use with a cutting unit consuming large amounts of industrial water and pure water. Although, above, a filter paper is wound into a filtering drum 5, it is also possible to wind a long wire into a filtering drum 5, for example a long wire obtained by twisting fibers of 2 to 20 A up to a thickness of 3 to 8 mm,

  in such a way that a wire 28 forming a certain layer 35 and a wire 28b forming the next layer intersect,

  shows me the perspective view of FIG 7, and the wire 28 is taken layer by layer It is also possible to prepare the auxiliary filter layer F isolated from the filter drum 5 This allows to do without devices to leave the layer In addition, although above the present invention has been described as applying to the filtering of waste water from cutting units for the manufacture of semiconductor devices, it may be applicable. to various water treatments, such as the treatment of waste water containing radioactive materials in nuclear power plants In this case, the filter quality of the filter paper used is chosen

  depending on the size of the particles in the wastewater.

  As the above description shows, the

  The present invention creates a small-size liquid filter for efficient continuous extraction of

  particles of a liquid for long periods of time, and which is in practice of great utility.

Claims (4)

  A liquid filter, comprising: a sealed container (10) having an inlet (10a) for receiving water to be filtered and an outlet (10 Ob) for discharging the filtered water; and filter means (1) provided in the container for cutting off a flow of water caused from the inlet to the outlet, so that unfiltered bypass water flow is captured by the wire means, characterized in that the filter means (1) is wound into a filtering drum (5) consisting of a number of filter layers and at the center of which is formed a cavity (5a), and that one end filter means (1) is wound on a winding spool (6) provided in the sealed container (10) separately from the filter drum for retaining auxiliary filter layers filter medium.   Filter according to Claim 1, characterized in that the winding spool (6) is provided in the cavity (5 a), the flow of water being directed from the inside of the filter drum (5) to the spool (5). 'outside filter drum.   Filter according to claim 1, characterized in that the winding spool (6) is provided outside the filter drum (5), the water flow being directed towards the filter outlet (1). )   towards the inside of the filter drum.   4. Filter according to claim 1, characterized in that the filtering means is a rolled filter paper (1). Filter according to Claim 1, characterized   in that the filtering means is a wire (28) wound in a filtering drum.