JP2007172994A - Static eliminator, static eliminating method, hdd device manufactured by using static eliminator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a static eliminator blowing air, which is lowered in contents of chemical substances such as acidic gas, alkaline gas, and organic gas contained in trace amounts to be used in a clean room/booth, toward a discharge electrode generating ions and feeding the generated ion wind to an object as a target of static elimination. <P>SOLUTION: This static eliminator has a blower feeding air to the object as a target of the static elimination, and a chemical filter removing the chemical substances included in air taken in by the blower and the discharge electrode generating ions neutralizing charges carried in a static eliminated part are provided in an air passage of the blower. The discharge electrode is arranged in the leeward of at least one chemical filter. An impression voltage V to the discharge electrode ranges from 1500 volt to 3000 volt. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a static eliminator used in a clean room, and in particular, chemical gases such as acid gas, alkaline gas, or organic gas, which are present in minute amounts in the air, generate positive and negative ions generated by the static eliminator. The present invention relates to a static eliminator that minimizes the amount of air contained therein.

  There are direct current (DC) application method, alternating current (AC) application method, soft X-ray irradiation method, etc. as the ion generation method of the static eliminator, neutralizing the static electricity charged on the object to be neutralized by the generated ions. Remove. In this type, many devices are provided with a dustproof filter so that dust mixed in the air to be taken in is not sent to the object to be discharged.

  When a GMR head is used as a magnetic head in a combination process of a magnetic head and a disk, which is the heart of a hard disk drive (HDD), performed in a dust-free environment such as a clean room or clean booth. In particular, it is desirable to work using a static eliminator so as not to cause damage due to static electricity.

  However, it has been found that when a conventional static eliminator is used, the magnetic head tends to be corroded.

  It is used in clean rooms as a method to reduce substances that are considered to cause corrosion in the airflow blown to the object to be discharged by the static eliminator, especially chemical substances such as chemical gases contained in trace amounts in the air. In addition to filters called HEPA and ULPA, it is considered effective to remove chemical substances in the air in the clean room as much as possible by installing chemical filters (for removing acid, alkali, and organic gas).

  However, removing chemical substances from the entire air in the clean room with a chemical filter is expensive considering the replacement frequency. Further, for example, ammonia gas is generated by an operator, so even if a chemical filter is attached to the entire clean room, the ammonia gas is difficult to remove.

  Therefore, for example, Japanese Patent Laid-Open No. 2002-75589 is provided with a filter for removing dust in the lee of a blower in a portable static eliminator that blows ionized air against an object to be discharged arranged in a local region. An apparatus is disclosed in which a discharge electrode is provided in the lee of the filter to remove dust in the air that is ionized by the filter, and the charge is removed without adhering foreign matter to the object to be discharged. The voltage applied to the discharge electrode provided in the apparatus described in the above publication is specifically described as ± 5000 volts.

However, if this static eliminator is used in a clean room, a large amount of dust is generated when air ionized by the discharge electrode is generated, and dust is generated from inside the clean room. It is thought that it will get dirty.
JP 2002-75589 A

  The purpose of the present invention is to use a discharge in which ions are generated in air having a reduced content of chemical substances such as acid gas, alkaline gas, or organic gas contained in a minute amount in the air used in a clean room or a clean booth. An object of the present invention is to provide a static eliminator that blows an electrode and sends generated ionic wind (flow of air containing ions) to an object to be eliminated.

  Invention of Claim 1 of this invention is a static elimination apparatus used in a clean room, Comprising: It has a blower which blows air to a to-be-eliminated object, and is contained in the air which the said blower takes in the air path of the said blower A chemical filter that removes the chemical substance to be discharged, and a discharge electrode that generates ions to neutralize the electric charge charged in the portion to be neutralized, and the lee of the at least one chemical filter And the voltage V applied to the discharge electrode is 1,500 volts ≦ | V | ≦ 3,000 volts.

  In clean rooms (or clean booths, including clean booths), an environment with a small amount of dust has been mainly pursued. However, in the air in clean rooms, gaseous chemistry is distinguished from conventional dust. Chemical substances including substances are contained, and even when manufacturing precision parts in a clean room, there are cases where chemical substances other than dust affect the quality.

  For example, in the process of combining a magnetic head and a disk of a hard disk drive (HDD) performed in a clean room with a small amount of dust, especially when a GMR head is used as the magnetic head, damage due to static electricity does not occur. In addition, work using the static eliminator is required.

  However, when the conventional static eliminator is used, it tends to cause corrosion of the magnetic head. This is considered to be caused by chemical substances including chemical gas contained in a minute amount in the air.

  When using a static eliminator so that the magnetic head is not damaged by static electricity in the process of combining the magnetic head and the disk, the magnetic head is smaller than the disk and close to it, so that the ion wind is applied only to the magnetic head. It is difficult to avoid hitting the disc.

  If the surface of the disk is covered with a protective film made of a wet polymer lubricant and dust or chemical gas components in the air are likely to adhere to it, the ion wind is forcibly applied. Substances generated by reaction of chemical gas components in the atmosphere, ions, moisture in the air, components of the protective film on the surface of the disk, and the like, attached to the disk. For example, a sulfuric gaseous substance present in a minute amount in the air, ions generated from the static eliminator, and moisture in the air may react to form sulfuric acid and adhere to the medium.

  When the disk rotates, the magnetic head floats, and when the disk stops rotating, the magnetic head is in contact with the disk surface. For this reason, when the magnetic head is in contact with the disk surface, the sulfuric acid material adhering to the disk surface is transferred to the surface of the magnetic head. A thin component having a low melting point of each layer forming the GMR head is easily corroded by the sulfuric acid material transferred to the surface of the magnetic head. Nitric acid-based substances are also considered to adhere to the disk surface.

  Thus, the substances generated on the disk surface that cause corrosion of the magnetic head due to chemical substances such as chemical gases contained in trace amounts in the air are not generated by the static eliminator itself. This is mainly because chemical substances in the air in the environment of use cause a chemical reaction with the positive and negative ions generated by the static eliminator, moisture in the air, etc., and the generated substances adhere to the disk surface. It is thought that.

  Therefore, in the present invention, dust in the air in the clean room is purified by a filter such as HEPA or ULPA provided in the clean room. Therefore, the static eliminator does not generate dust as much as possible. An ion wind whose amount of the chemical substance of the kind to be applied is less than a desired amount is applied to the object to be neutralized.

  For this reason, the filter for removing dust in the air is not considered first, but dust generated by applying a voltage to the discharge electrode with a chemical filter that reduces the target type of chemical substance as much as possible. Try to suppress as much as possible.

  Gaseous chemical substances in the air include acid (sulfuric acid, nitric acid, chlorine, etc.), alkaline (ammonia, etc.) and organic (siloxane, etc.). Chemical filters for removing these gaseous chemical substances include those for acidic gas, alkaline gas, and organic gas, which are selected alone or in combination according to the purpose.

  According to the first aspect of the present invention, a chemical filter for removing a target type of chemical substance is mounted for each purpose from the air in the clean room taken in by the static eliminator, and + and − ions are applied at an applied voltage. In order to suppress dust generated by applying a voltage to the generated discharge electrode, the voltage V applied to the discharge electrode is V = ± 10,000 volts used in a normal static eliminator, or V = ± With respect to an applied voltage of 5,000 volts, in the present invention, the applied voltage is 1,500 volts ≦ | V | ≦ 3,000 volts, preferably V = ± 2,000 volts.

  Contamination of the discharge electrode is caused by a mixture of fine dust in the air and gaseous chemical substances adhering to the discharge electrode, and burning by applying a high voltage to the discharge electrode. It was found that by generating an ion wind by discharging in the electrode, the contamination of the electrode can be remarkably reduced and the wear of the discharge electrode can be significantly suppressed. Furthermore, since a stable ion wind can be generated even with a voltage applied to the discharge electrode lower than the conventional voltage, the generation of dust from the discharge electrode is suppressed by lowering the voltage applied to the discharge electrode. Compared with the static eliminator, the amount of dust generated is greatly reduced.

  In the static eliminator according to the present invention, air from which dust and chemical substances have been removed as much as possible is sent to the discharge electrode, so that the wear of the discharge electrode is suppressed, and the amount of dust generated from the discharge electrode is reduced. Since ions can be stably generated even when the voltage applied to the discharge electrode is lower than that of the static eliminator, the amount of dust generated is further reduced.

  According to the present invention, the air in which the chemical substance mainly the gaseous chemical substance in the air is removed by the chemical filter wraps the discharge electrode, thereby reducing the contamination of the surface of the discharge electrode and being stable even at a low voltage. Since the electrode discharge is obtained, the amount of the discharge electrode is reduced by reducing the voltage applied to the discharge electrode. In fact, the wear of the discharge electrode is greatly improved, and the cleaning cycle of the discharge electrode is, for example, sufficient if it is performed once every week for 2 weeks to once a month.

  Among the general static eliminators, especially in the DC application type static eliminator, there are a plus electrode and a minus discharge electrode, and a high voltage, for example, 8,000 volts or more is applied to the discharge electrode to corona discharge. To ionize oxygen, nitrogen, water, etc. in the air. The ions are discharged to the charged object as an ion wind with a fan. Normally, it is difficult to make positive ions, so when a further voltage is applied to the discharge electrode, the consumption of the discharge electrode increases rapidly, and a large amount of fine particles scattered from the discharge electrode cause particles caused by chemical substances in the air. It adheres to the surface of non-charged material and contaminates the surface of non-charged material.

  In the present invention, even when the voltage applied to the discharge electrode is V = ± 3,000 volts, the discharge electrode is consumed and becomes dust and is discharged into the air in the clean room. As a result of measuring the increase in the amount of dust, It was found that the static eliminator according to the present invention can be used in a clean room within the practical range.

  As described above, by using the static eliminator of the present invention, the ion wind from which chemical substances in the air are removed as much as possible is sent to the object to be neutralized, thereby reducing the wear of the discharge electrode that generates ions. In addition, since stable discharge can be performed at a low voltage, preferably, the amount of dust generated is greatly reduced by discharging at | V | ≦ 2,000 volts.

  The static eliminator of the present invention does not have a function of taking in air in a clean room and removing dust generated from the static eliminator. Thereby, since there is little wind pressure loss if it does not have a dust removal filter, the kind or number of chemical filters to mount can be increased.

  The invention according to claim 2 of the present invention is the static eliminator according to claim 1, wherein the chemical filter removes corrosive gas that causes the object to be neutralized to corrode.

  According to invention of Claim 2, the chemical filter with which a static elimination apparatus is equipped can be selected according to the objectives for acidic gas, alkaline gas, and organic gas. Among these, in particular, the apparatus includes a chemical filter that removes gaseous chemical substances in the air that cause the object to be discharged to corrode. Furthermore, it is equipped with a filter that is effective for minimizing the consumption and wear of the discharge electrode used in the static eliminator, so that the static eliminator with less dust emission and a long maintenance cycle for cleaning and replacement of the discharge electrode is provided. It can be.

  The invention according to claim 3 of the present invention is the static eliminator according to claim 1 or 2, wherein the chemical filter uses an ion exchange nonwoven fabric.

  According to the invention described in claim 3 of the present invention, since the material of the chemical filter is a non-woven fabric, it is lightweight and has low wind pressure loss, and is suitable for removing chemical substances in air of the type desired to be removed. can do.

  The invention according to claim 4 of the present invention is an HDD device manufactured using the static eliminator according to claims 1 to 3.

  Further, the invention according to claim 5 of the present invention is a method for removing static electricity in a clean room, wherein the chemical contained in the air taken in by the blower into the air passage of the blower that blows air against the static electricity to be removed. Providing a chemical filter for removing a substance and a discharge electrode for generating ions for neutralizing charges charged in the portion to be neutralized, and disposing the discharge electrode in the lee of at least one of the chemical filters; The voltage V applied to the discharge electrode is 1,500 volts ≦ | V | ≦ 3,000 volts.

  By removing chemical substances including gaseous chemical substances in the air in the clean room with the static eliminator according to the present invention, the type of the chemical filter to be used is changed or combined, so that the air in the clean room is in the air. It is possible to send air from which a desired chemical substance to be removed is removed as much as possible to the discharge electrode and ion wind to the object to be discharged.

  Furthermore, by reducing the consumption and wear of the discharge electrode, it is possible to send ion wind with a small amount of dust to the object to be discharged, and to increase the cleaning and replacement cycle of the discharge electrode to reduce the frequency of maintenance. Can do.

  FIG. 1 is a diagram showing an embodiment of a static eliminator according to the present invention. In FIG. 1, the inside of the static elimination apparatus main body 1 takes in air, the fan 1-1 for blowing out an ion wind, the ion generation part 1-2 provided with the discharge electrode (illustration omitted) which generate | occur | produces ion, static elimination apparatus operation Part 5, ion wind outlet 6, and power supply part 8. The chemical filter storage unit 2 is attached to the left side of FIG. 1 without any gap with the static eliminator main body 1 but with a detachable fixture (not shown), and takes in the air in the clean room from the air intake port 2-1. Then, an ion wind is blown out from the ion wind outlet 6, and an object to be removed (not shown) is installed at a position indicated by the measurement point 9, neutralizing static electricity generated by the object to be removed and removing electricity. L in the figure indicates the distance from the ion wind outlet 6 to the measurement point 9.

  In the chemical filter storage unit 2, one or more kinds of chemical filters (not shown) for removing chemical substances including a desired gaseous chemical substance are stored. In this embodiment, for example, an EPIX trace gas removal filter (manufactured by Ebara Seisakusho) made of ion exchange fiber is used.

When the chemical filter is attached, both the air volume and the wind speed of the ion wind are reduced due to the wind pressure loss, as in the case of attaching the dust filter. In order not to take a long time to neutralize the static electricity of the object to be neutralized, which is the basic performance of the static eliminator, the surface wind speed of the ion wind blown from the ion outlet 6 is 2 m / sec or more and the air volume is 1 m ³ / The shape of the fan 1-1, the type of the motor (not shown) that rotates the fan, and the configuration of the chemical filter were optimized so as to ensure at least min.

  For example, a material such as tungsten, SUS, titanium, or polysilicon is used for the electrode member of the discharge electrode of the ion generator 1-2. These have a high melting point and can withstand high temperatures due to high voltages. However, since both are hard and brittle materials, they become ultrafine particles due to high voltage, and the tip of the member itself is scraped and scattered. The particles or the particles and the chemical substance adhere to the object to be discharged. As the high voltage is applied, scattering increases and the amount of deposits on the object to be discharged increases.

  FIG. 2 is a diagram showing an embodiment (outside view) of the static eliminator according to the present invention. In the static eliminator main body 1, a chemical filter storage unit 2 storing a chemical filter (not shown) is detachably attached to the static eliminator main body 1 by two chemical filter storage unit attachments 2-2, but closely attached without any gap. It is attached in a state. The air intake port 2-1 of the chemical filter storage unit 2 is located on the left side of the figure.

  The static eliminator main body 1 is fixed to the static eliminator main body support 3 with a desired inclination by the static eliminator main body tilt adjustment knob 4. The static eliminator operation unit 5 includes a power ON / OFF switch, an ion air volume adjustment volume, an ion balance adjustment volume, a discharge electrode cleaning notification lamp, a voltage adjustment volume applied to the discharge electrode, and the like. The ion balance sensor is built in, for example, the ion wind outlet 6.

  FIG. 3 is a diagram showing another embodiment of the static eliminator according to the present invention. Compared to FIG. 1, an example in which another nitric acid removing filter 10 is provided on the lee of the static eliminator main body 1 is shown.

  In the following description, the ion generation method of the static eliminator in the embodiment according to the present invention adopts the AC application method, and the discharge electrode uses eight tungsten electrodes. The applied voltage is ± 1800 V, and the current value is about 200 μA.

  In FIG. 1, an ion balance measuring device 713 (manufactured by Sumitomo 3M Limited) was set at a measurement point 9 of L = 30 cm. Ion balance and static elimination time were measured with this measuring instrument. Furthermore, dust generation from the slow current device was measured with a dust meter KM-20 (manufactured by Rion Co., Ltd.). These measurement results are shown in Table 1.

  In Table 1, the measured value in the column of a general static eliminator is an example of the measured value in a commercially available static eliminator measured as a reference for comparison with the static eliminator of the present invention (hereinafter referred to as the present static eliminator). . The number of dusts is an average value of measurement values obtained by repeating measurement for one minute with a dust meter four times. The electrode contamination time is an interval of days when the discharge electrode needs to be cleaned.

  From this table, it can be seen that by installing a chemical filter on the windward side of the ion generator 1-2, the electrode contamination time until the electrode is contaminated and needs to be cleaned is greatly improved.

  Next, a disk with a diameter of 3 inches was placed almost perpendicular to the ion wind at a measurement point 9 with L = 20 cm. In this state, an ion wind of the static eliminator was blown onto the disk for 20 hours. The disk was immersed in ultrapure water to extract ions adhering to the disk, and then anion and cation were analyzed with an ion chromatograph (Yokogawa Electric). The results are shown in Table 2.

  In Table 2, the reference disk column shows reference values for the reference disk when the ion wind from the static eliminator is not applied to the disk. Moreover, the measured numerical value was each displayed by the number of micrograms per disk.

  In the case of this example, when the ion wind from the static eliminator is applied to the disk, sulfate ions are reduced compared to the case where the ion wind from a general static eliminator is applied. It can be seen that ammonia ions are also low.

  Next, as shown in FIG. 3, a nitrate removal filter 10 for removing nitrate gas substances in the chemical filter is installed on the ion wind outlet side of the static eliminator for the purpose of further removing nitrate ions. did. The results are shown in Table 3. The ion balance, static elimination time, and the number of dusts are the same as the measurement conditions in Table 1, and the measurement conditions for ions attached to the disk are the same as in Table 2.

  From Table 3, it can be seen that nitric acid ions are hardly attached to the disk surface. Moreover, it seems that the ion balance which shows the performance as a static elimination apparatus, and static elimination time are also satisfactory.

  Furthermore, with the same chemical filter configuration as in Table 3, the dust generation and the amount of sulfate and nitrate ions attached to the disk surface when the applied voltage to the electrode of this static eliminator was changed from ± 1800V were investigated. Table 4 shows the results. The current value is 200 μA.

In Table 4, the measurement of dust is the same as the measurement condition in Table 1, and the measurement condition of ions attached to the disk surface is the same as the measurement condition in Table 2.
However, the number of dusts having a diameter of 0.01 μm to 0.1 μm is an average value of measured values obtained by measuring four times for 12 minutes with a condensation nucleus counter (CNC).

  From Table 4, when the applied voltage to the discharge electrode is increased from ± 1800V to ± 4500V, ± 8500V, the number of dust having a diameter of 0.01 μm to 0.1 μm increases rapidly, but it exceeds 0.1 μm. The number of dust with a diameter does not increase in this range. It can also be seen that both nitrate ions and sulfate ions adhering to the disk surface are low.

Is an embodiment of a static eliminator according to the present invention. Is an embodiment (external view) of the static eliminator according to the present invention. Is another embodiment of the static eliminator according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Static elimination apparatus main body 2 Chemical filter storage unit 3 Static elimination apparatus main body support tool 4 Static neutralization apparatus main body inclination adjustment knob 5 Static elimination apparatus operation part 6 Ion wind blower outlet 7 Power supply cord 8 Power supply part 9 Measuring point 10 Nitric acid removal filter

Claims (5)

A static eliminator used in a clean room,
It has a blower that blows air to the object to be discharged,
In the air path of the blower,
A chemical filter for removing chemical substances contained in the air taken in by the blower;
A discharge electrode that generates ions to neutralize the charge charged in the portion to be neutralized and neutralize the charge,
Disposing the discharge electrode leeward of the at least one chemical filter;
The charge removal device according to claim 1, wherein the voltage V applied to the discharge electrode is 1,500 volts ≦ | V | ≦ 3,000 volts.   2. The static eliminator according to claim 1, wherein the chemical filter removes corrosive gas that causes the object to be neutralized to corrode.   The static eliminator according to claim 1 or 2, wherein the chemical filter uses an ion exchange nonwoven fabric.   An HDD device manufactured using the static eliminator according to claim 1.   A method for removing static electricity in a clean room, wherein a chemical filter that removes chemical substances contained in the air taken in by the blower into an air passage of a blower that blows air to the static electricity and the charge removal portion are charged. And a discharge electrode that generates ions to neutralize the charge that is neutralized, and the discharge electrode is disposed leeward of at least one of the chemical filters, and the applied voltage V to the discharge electrode is 1,500 volts ≦ | V | ≦ 3,000 volts.

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