Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28D—WORKING STONE OR STONE-LIKE MATERIALS
  • B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
  • B28D5/0058—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material
  • B28D5/0076—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material for removing dust, e.g. by spraying liquids; for lubricating, cooling or cleaning tool or work
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B27/00—Other grinding machines or devices
  • B24B27/06—Grinders for cutting-off
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  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M125/00—Lubricating compositions characterised by the additive being an inorganic material
  • C10M125/26—Compounds containing silicon or boron, e.g. silica, sand
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  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M173/00—Lubricating compositions containing more than 10% water
  • C10M173/02—Lubricating compositions containing more than 10% water not containing mineral or fatty oils
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  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2201/00—Inorganic compounds or elements as ingredients in lubricant compositions
  • C10M2201/06—Metal compounds
  • C10M2201/062—Oxides; Hydroxides; Carbonates or bicarbonates
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  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/02—Hydroxy compounds
  • C10M2207/021—Hydroxy compounds having hydroxy groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/022—Hydroxy compounds having hydroxy groups bound to acyclic or cycloaliphatic carbon atoms containing at least two hydroxy groups
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/121—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms
  • C10M2207/124—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms containing hydroxy groups; Ethers thereof
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/125—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids
  • C10M2207/127—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids polycarboxylic
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/10—Macromolecular compoundss obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/103—Polyethers, i.e. containing di- or higher polyoxyalkylene groups
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/10—Macromolecular compoundss obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/103—Polyethers, i.e. containing di- or higher polyoxyalkylene groups
  • C10M2209/104—Polyethers, i.e. containing di- or higher polyoxyalkylene groups of alkylene oxides containing two carbon atoms only
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/10—Macromolecular compoundss obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/103—Polyethers, i.e. containing di- or higher polyoxyalkylene groups
  • C10M2209/105—Polyethers, i.e. containing di- or higher polyoxyalkylene groups of alkylene oxides containing three carbon atoms only
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/10—Macromolecular compoundss obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/103—Polyethers, i.e. containing di- or higher polyoxyalkylene groups
  • C10M2209/108—Polyethers, i.e. containing di- or higher polyoxyalkylene groups etherified
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
  • C10M2215/04—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to acyclic or cycloaliphatic carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
  • C10M2215/04—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2215/042—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to acyclic or cycloaliphatic carbon atoms containing hydroxy groups; Alkoxylated derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2217/00—Organic macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2217/02—Macromolecular compounds obtained from nitrogen containing monomers by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2217/028—Macromolecular compounds obtained from nitrogen containing monomers by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a nitrogen-containing hetero ring
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2229/00—Organic macromolecular compounds containing atoms of elements not provided for in groups C10M2205/00, C10M2209/00, C10M2213/00, C10M2217/00, C10M2221/00 or C10M2225/00 as ingredients in lubricant compositions
  • C10M2229/02—Unspecified siloxanes; Silicones
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2020/00—Specified physical or chemical properties or characteristics, i.e. function, of component of lubricating compositions
  • C10N2020/01—Physico-chemical properties
  • C10N2020/011—Cloud point
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2020/00—Specified physical or chemical properties or characteristics, i.e. function, of component of lubricating compositions
  • C10N2020/01—Physico-chemical properties
  • C10N2020/04—Molecular weight; Molecular weight distribution
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/02—Pour-point; Viscosity index
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/04—Detergent property or dispersant property
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/12—Inhibition of corrosion, e.g. anti-rust agents or anti-corrosives
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/28—Anti-static
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/20—Metal working
  • C10N2040/22—Metal working with essential removal of material, e.g. cutting, grinding or drilling
• • C—CHEMISTRY; METALLURGY
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  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/32—Wires, ropes or cables lubricants

Definitions

• the present invention relates to a water-soluble working fluid for a fixed-abrasive wire saw.
• the diameter of silicon wafers has been increased rapidly to reduce the manufacturing cost of semiconductor devices, and it has become important to improve the cutting technique of the silicon wafers.
• the cutting technique there is a cutting method using a wire tool (wire saw), which causes less cutting loss and exhibits good processing efficiency.
• wire tool wire saw
• Patent Document 1 discloses a fixed abrasive wire saw having abrasive grains of 30 to 60 ⁇ m fixed by resin bond.
• the fixed abrasive wire saw is moved at a speed of 1000 to 2500 m/min to cut a brittle material, thereby enabling highly efficient cut processing.
• a hard deposit (hereinafter sometimes referred to as a "hard cake") is created in a groove of a main roller onto which a wire is to be hooked, causing skipping of the wire (causing the wire to come off the groove), and so on.
• an object of the present invention is to provide a water-soluble working fluid for a fixed abrasive wire saw which can be inhibited from increasing its viscosity when mixed with cut debris and can prevent clogging of a pipe of equipment and generation of a hard cake that are caused by the cut debris.
• a first aspect of the present invention is a water-soluble working fluid for a fixed-abrasive wire saw, the water-soluble working fluid comprising: (C) a carboxylic acid; (D) a compound which shows basicity on dissolution in water; and (E) water, wherein an electrical conductivity at 25°C of the water-soluble working fluid is 300 ⁇ S/cm or more and 3000 ⁇ S/cm or less; a pH at 25°C of the water-soluble working fluid is 5 or more and 10 or less; and a viscosity of a simulated fluid formed by adding 10 mass % of a silicon powder having an average particle size of 1.5 ⁇ m to the water-soluble working fluid and stirring a resultant mixture is less than 30 mPa ⁇ s at 25°C.
• the "viscosity” refers to a viscosity measured by a Brookfield-type viscometer.
• the “average particle size” refers to an average particle size measured by using a laser diffraction/scattering type particle size distribution measuring device "LA910" manufactured by HORIBA.
• the working fluid of the first aspect of the present invention preferably further comprises (A) at least one nonionic surfactant selected from copolymers of an alcohol, ethylene oxide, and propylene oxide, and polyoxyalkylene glycols.
• the working fluid of the first aspect of the present invention preferably further comprises (B) a glycol.
• a second aspect of the present invention is a water-soluble working fluid for a fixed-abrasive wire saw, the water-soluble working fluid comprising: (A) 0.1 mass % or more and 8 mass % or less of at least one nonionic surfactant selected from copolymers of an alcohol, ethylene oxide, and propylene oxide, and polyoxyalkylene glycols; (B) 0.1 mass % or more and 80 mass % or less of a glycol; (C) 0.01 mass % or more and 5 mass % or less of a carboxylic acid; (D) 0.01 mass % or more and 7 mass % or less of a compound which shows basicity on dissolution in water; and (E) water, wherein an electrical conductivity at 25°C of the water-soluble working fluid is 300 ⁇ S/cm or more and 3000 ⁇ S/cm or less; a pH at 25°C of the water-soluble working fluid is 5 or more and 10 or less; and a viscosity of a simulated fluid formed
• the working fluids of the first and the second aspects of the present invention preferably have a surface tension at 25°C of 20 mN/m or more and 50 mN/m or less.
• the working fluids of the first and the second aspects of the present invention preferably contain 10 mass % or more and 99.7 mass % or less of the (E) water, based on a total mass of the working fluid as 100 mass %.
• a water-soluble working fluid for a fixed abrasive wire saw which can be inhibited from increasing its viscosity when mixed with cut debris and can prevent clogging a pipe of equipment and generation of the hard cake that are caused by the cut debris.
• the water-soluble working fluid for a fixed abrasive wire saw of the present invention has an electrical conductivity at 25 °C of 300 ⁇ S/cm or more and 3000 ⁇ S/cm or less.
• the upper limit of the electrical conductivity is preferably no more than 2000 ⁇ S/cm, and more preferably no more than 1000 ⁇ S/cm.
• the electrical conductivity indicates how well electricity can be conducted, and is defined as the reciprocal of electrical resistivity.
• concentration of an ionic substance contained in the working fluid As the concentration of an ionic substance contained in the working fluid is higher, the electrical conductivity of the working fluid increases and better conducts electricity. Further, as the concentration of an ionic substance contained in the working fluid is higher, particulates (cut debris) having an electrical charge tend to agglomerate in the working fluid more easily. Namely, as the electrical conductivity of the working fluid increases, the apparent particle size of the cut debris mixed in the working fluid becomes larger and the cut debris precipitate more easily. At this time, since the cut debris precipitate in a sterically-bulky state, it is seen to be unlikely that a hard cake is generated. Further, the cut debris can precipitate faster when it is in the agglomerated state, and it can be easily separated from the working fluid by means of centrifugal separation or the like.
• the electrical conductivity of the working fluid of the present invention can be adjusted by an amount of a substance ionized on dissolution in water added to the working fluid.
• the electrical conductivity of the working fluid can be adjusted appropriately by adjusting the additive amount of the below described (C) component (a carboxylic acid) or the additive amount of the below described (D) component (a compound which shows basicity on dissolution in water), to the working fluid.
• the working fluid of the present invention may be diluted with water when used, but in this case as well, the electrical conductivity of the working fluid after dilution is preferably in the range given above.
• a viscosity of a fluid (simulated fluid) formed by dispersing a predetermined silicon powder in the working fluid of the present invention is preferably 1 mPa ⁇ s or more and less than 30 mPa ⁇ s at 25 °C, more preferably 1 mPa ⁇ s or more and 20 mPa ⁇ s or less at 25 °C, and still more preferably 1 mPa ⁇ s or more and 15 mPa ⁇ s or less at 25 °C.
• the viscosity of the simulated fluid is based on measurement of a viscosity of a simulated fluid obtained by: adding 10 mass % of a silicon powder (particle size: 1.5 ⁇ m) to the working fluid of the present invention; mixing them by stirring; thereafter putting a stainless steel ball (2 mm in diameter) into a resultant mixture; stirring the mixture at 1000 rpm for 10 hours; and filtering off the stainless steel ball. If the viscosity of the working fluid described above is already too high, the viscosity of the simulated fluid containing the silicon powder will also be inevitably high. The viscosity of the working fluid and the simulated fluid can be measured by a Brookfield-type viscometer.
• a pH of the working fluid of the present invention is 5 or more and 10 or less at 25°C.
• metal corrosivity of the working fluid becomes high, likely causing corrosion of a metal component of equipment or a wire saw brought into contact with the working fluid.
• the metal corrosivity of the working fluid can be easily inhibited by setting the pH of the working fluid to be 5 or more at 25°C, though it depends on such factors as the amount of water contained in the working fluid.
• the pH of the working fluid of the present invention is preferably 6 or more at 25°C, and more preferably 7 or more at 25°C.
• the pH of the working fluid is over 10
• the reactivity of the working fluid with the cut debris (silicon) mixed in the working fluid will rise, thus likely causing generation of hydrogen by reaction of the working fluid with the cut debris, or likely causing significant increase in the viscosity of the working fluid during processing.
• the pH of the working fluid of the present invention can be appropriately adjusted by the blending amount of the (B) component (a glycol), the (C) component (a carboxylic acid), and the (D) component (a compound which shows basicity on dissolution in water) that are described below.
• the viscosity of the working fluid of the present invention can also be adjusted by adding another additive (e.g. a pH adjuster).
• the working fluid of the present invention may be diluted with water when used, but in this case as well the pH of the working fluid after dilution is preferably in the range described above.
• the inventors have found that the conventional working fluids have insufficient wettability on a wire used and insufficient permeability into a gap in a workpiece, and that the amount of the working fluids to reach a portion to be processed (i.e. a portion of the workpiece to be brought into contact with the wire) is insufficient, thus sometimes causing degradation of the cutting performance.
• a portion to be processed i.e. a portion of the workpiece to be brought into contact with the wire
• the surface tension of the working fluid is too high, the wettability and the permeability of the working fluid deteriorate, likely preventing the working fluid from reaching the portion to be processed.
• the portion to be processed ends up being cut in a dry state.
• the surface tension of the working fluid of the present invention is preferably 50 mN/m or less at 25°C, more preferably 45 mN/m or less at 25°C, and still more preferably 40 mN/m or less at 25°C.
• the surface tension of the working fluid of the present invention is preferably 20 mN/m or more at 25°C, and more preferably 30 mN/m or more at 25°C.
• the surface tension of the working fluid of the present invention can be adequately adjusted for example by the blending amount of the (A) component or a defoaming agent described below.
• the working fluid of the present invention may be diluted with water when used, but in this case as well the surface tension of the working fluid after dilution is preferably in the range given above.
• the working fluid of the present invention may contain the components described below for example.
• the working fluid of the present invention may contain at least one nonionic surfactant selected from copolymers of an alcohol, ethylene oxide, and propylene oxide, and polyoxyalkylene glycols.
• the (A) component contained in the working fluid the surface tension of the working fluid can be lowered, and the wettability and the permeability of the working fluid can be improved.
• an alcohol having a carbon number of 8 to 12 can be employed for example.
• polyoxyalkylene glycols mentioned above include: polyethylene glycol; polypropylene glycol; and a copolymer of polyoxyethylene and polyoxypropylene.
• a mass-average molecular weight of the polyoxyalkylene glycols is preferably 10000 or less, more preferably 5000 or less, and still more preferably 3500 or less.
• the working fluid of the present invention may be in the form of being diluted with water as necessary based on the working conditions of the cutting process. That is, the working fluid of the present invention may be made by preparing a concentrated composition formed of components in the working fluid of the present invention other than water and diluting the concentrated composition with water at a work site or the like.
• the working fluid of the present invention may be made in a highly concentrated form (that is, the working fluid of the present invention may be made using a small amount of water) to be used as it is or to be further diluted with water, depending on the working conditions of the cut processing.
• the lower limit of the content of the (A) component is preferably no less than 0.1 mass %, more preferably no less than 0.2 mass %, and still more preferably no less than 0.5 mass %, based on the total mass (100 mass%) of the working fluid of the present invention.
• the upper limit thereof is preferably no more than 0.8 mass %, more preferably no more than 0.7 mass %, and still more preferably no more than 0.6 mass %, based on the total mass (100 mass%) of the working fluid of the present invention.
• the working fluid of the present invention may further contain a glycol as the (B) component.
• a glycol as the (B) component.
• glycols propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol are preferred; and dipropylene glycol and diethylene glycol are especially preferred. They may be used alone or in combination. A copolymer formed of two or more of the above may also be used.
• a mass-average molecular weight of the above glycols is preferably 100 or more and 700 or less, and more preferably 100 or more and 200 or less.
• the upper limit of the content of the (B) component is preferably no more than 80 mass %, and more preferably no more than 70 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• carboxylic acid as the (C) component examples include citric acid, succinic acid, lactic acid, malic acid, adipic acid, oxalic acid, dodecanedioic acid, and acetic acid.
• citric acid and succinic acid are preferred, and citric acid is more preferred. They may be used alone or in combination.
• the upper limit of the content of the (C) component is preferably no more than 5 mass %, more preferably no more than 3 mass %, and still more preferably no more than 2 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• the working fluid of the present invention also contains, as the (D) component, a compound which shows basicity on dissolution in water (hereinafter sometimes referred to as a "basic compound").
• the (D) component a compound which shows basicity on dissolution in water
• Including a predetermined amount of the (D) component in the working fluid of the present invention enables, in combination with the (C) component described above, such advantageous effects that: the pH and the electrical conductivity of the working fluid of the present invention can be adjusted; fluctuation of the pH of the working fluid of the present invention during cut processing can be reduced; metal corrosivity of the working fluid can be reduced; and other components can be dissolved into the working fluid of the present invention stably.
• the basic compound as the (D) component include: compounds containing alkali metal elements such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate; and amines such as triethanolamine, triisopropanolamine, ethylenediamine, N-(2-aminoethyl)-2-aminoethanol, and N-( ⁇ -aminoethyl)ethanol amine. They may be used alone or in combination.
• alkali metal elements such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate
• amines such as triethanolamine, triisopropanolamine, ethylenediamine, N-(2-aminoethyl)-2-aminoethanol, and N-( ⁇ -aminoethyl)ethanol amine. They may be used alone or in combination.
• the lower limit of the content of the (D) component is preferably no less than 0.01 mass %, and more preferably no less than 0.1 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• the upper limit thereof is preferably no more than 0.7 mass %, more preferably no more than 0.6 mass %, and still more preferably no more than 0.5 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• the upper limit of the content of the (D) component is preferably no more than 7 mass %, more preferably no more than 6 mass %, and still more preferably no more than 5 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• the working fluid of the present invention may contain a salt formed from the (C) component and the (D) component, instead of the (C) component and the (D) component described above.
• the salt is preferably contained in the amount described above in terms of the (C) component and the (D) component.
• Specific examples of the salt include alkali metal salts of carboxylic acids and amine salts of carboxylic acids.
• the working fluid of the present invention contains water as the (E) component.
• the kind of water is not particularly limited and may be distilled water, tap water, etc.
• water with high electrical conductivity for example water with high hardness
• a concentration of ion (hardness) in tap water varies among areas or countries.
• the workpiece is silicon
• the water in the working fluid and the cut debris may react with each other to generate hydrogen gas. Since the amount of water in the conventional aqueous working fluid cannot be increased easily, the problem of the cooling ability thereof has not yet been solved fundamentally.
• hydrogen gas is generated by reaction of the cut debris mixed in the working fluid with the water in the working fluid
• the working fluid takes in bubbles at a time of being supplied by a pump.
• the amount of the working fluid supplied becomes instable or the specific weight of liquid decreases due to the bubbles taken in, therefore leading to such problems that a wire machine which controls the working fluid by the specific weight of liquid detects the abnormality and stops the processing. There is also a risk that the hydrogen gas generated explodes due to static electricity.
• the working fluid of the present invention it is possible to inhibit reaction between the working fluid and the cut debris by including each of the components described above and also setting the pH at the predetermined value mentioned above. Therefore, the amount of water contained in the working fluid can be increased to improve the cooling ability of the working fluid. That is, according to the working fluid of the present invention, it is possible to attain both inhibition of the hydrogen generation and improvement of the cooling ability.
• the corrosion can be inhibited by including a predetermined amount of the (B) component and the (C) component, or adjusting the pH of the working fluid in the predetermined range given above. Therefore, the amount of water contained in the working fluid can be increased to improve the cooling ability of the working fluid. That is, according to the working fluid of the present invention, it is possible to attain both inhibition of the corrosion and improvement of the cooling ability.
• the amount of the water is 100 %, that is, in a case of pure water, it is unsuitable as a working fluid in view of the wettability and the permeability.
• the cooling ability of the working fluid is better as the amount of water contained in the working fluid is larger.
• the water-soluble polymer that can be used in the present invention is not particularly limited and may be selected from those used in the conventional working fluids. Examples thereof include polyvinylpyrrolidone and a copolymer having a structural unit derived from vinylpyrrolidone.
• the content of the water-soluble polymer may be adequately determined within the range that can realize the above advantageous effect enabled by inclusion of the water-soluble polymer, does not hinder the advantageous effects of other components, and does not cause negative influence on the working fluid.
• a known defoaming agent may be used without particular limitations. However, it is preferable to employ a defoaming agent that can be dispersed in the working fluid stably.
• the upper limit of the content of the defoaming agent is preferably no more than 0.6 mass %, more preferably no more than 0.5 mass %, and still more preferably no more than 0.4 mass %, based on the total mass (100 mass %) of the working fluid of the present invention.
• the working fluid of the present invention may contain other components that are not described above.
• Various kinds of additives which do not cause negative influences on the workpiece, such as corrosion and discoloration of the workpiece and which do not affect stability of a system after mixing, may be added to the working fluid of the present invention within the range that does not affect the processibility.
• examples of such additives include a viscosity adjuster, a pH adjuster, and an anti-oxidation agent.
• the viscosity adjuster, the pH adjuster, and the anti-oxidation agent are not particularly limited and known ones may be used. However, those that are soluble in water are preferred.
• Water-soluble working fluids for a fixed-abrasive wire saw of the present invention (Examples 1 to 4) and water-soluble working fluids for a fixed-abrasive wire saw not being the present invention (Comparative Examples 1 to 13) were made such that the working fluids had the respective compositions shown in Tables 1 and 2.
• the content of each component shown in Tables 1 and 2 is represented in mass %.
• Comparative Example 9 is a working fluid containing 10 mass % of a synthetic fluid produced by YUSHIRO CHEMICAL INDUSTRY CO., LTD. and 90 mass % of water.
• the "C10alcohol:EOPO" shown in Tables 1 and 2 refers to a copolymer of an alcohol having a carbon number of 10, ethylene oxide, and propylene oxide.
• the "electrical conductivity” shows the result of the electrical conductivity at 25°C of each working fluid measured by using a conductivity meter ES-51 manufactured by HORIBA.
• the "viscosity of simulated fluid” shows the measurement result obtained by the following procedure. First, a simulated fluid was made by: adding 10 mass % of a silicon powder (average particle size: 1.5 ⁇ m) to each of the working fluids; mixing them by stirring; thereafter putting a stainless steel ball (2 mm in diameter) into each of the resultant mixtures; and stirring the mixtures at 1000 rpm for 10 hours.
• Examples 1 to 4 exhibited favorable results in each of the evaluations on the hard cake, precipitation performance, and corrosivity. Additionally, in Examples 1 to 4, the amount of hydrogen generated was small and the viscosity of the simulated fluids was low. On the other hand, as shown in Tables 1 and 2, Comparative Examples 1 to 13 had poor results in any one of the evaluations on the hard cake, the precipitation performance and the corrosivity, had a high viscosity of the simulated fluids was high, or had a large amount of hydrogen generated.
• the water-soluble working fluid for a fixed-abrasive wire saw of the present invention can be used when cutting a silicon wafer by using a fixed-abrasive wire saw.

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