JP2012206870A - Method for producing spherical silica powder and method for producing semiconductor sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method which can produce silica powder of a low uranium concentration at a low cost.SOLUTION: The method includes a grinding process in which ground quartz rocks of 1 ppb or below uranium content are made to collide mutually in high velocity gas to be ground into a ground product and a melting spheroidization process in which the ground product is put into a flame to melt and spheroidize it. In other words, the mingling of uranium from a grinder can be prevented by adopting a method for carrying out a grinding operation without contact with the grinder to the utmost. Especially, the grinding process, by being carried out in a grinding container lined with an elastomer, can reduce the possibility of the mingling from the wall of the container which occurs by the collision of silica powder in a high velocity air current with the wall of the grinding container of the grinder. Since the removal of uranium from a polymer material is relatively simple, even if the polymer material is mixed, the mingling of uranium can be suppressed, and if the polymer material is mixed into the ground product, it is oxidized and scattered in a following melting spheroidization process so that there may be no problem.

Description

  The present invention relates to a method for producing a spherical silica powder capable of obtaining a high-purity spherical silica powder and a method for producing a semiconductor encapsulant using the production method.

  In many cases, a semiconductor sealing material is blended with spherical silica powder for the purpose of imparting high performance. In this case, the presence of impurities contained in the spherical silica powder greatly affects the semiconductor to which the semiconductor sealing material is applied.

  Conventionally, as a method for producing high-purity silica as a raw material for high-purity spherical silica powder, there has been a method for controlling the impurity concentration in silica powder produced by using high-purity natural silica ( Patent Document 1). Patent Document 1 discloses a method for producing a fused silica powder using silica with an uranium content of 0.1 ppb as an impurity.

Japanese Patent No. 3434047

  However, even if the required purity of the silica is secured, impurities derived from the wear of the pulverizing apparatus that are in contact with the powder in the process of being pulverized may be mixed. In particular, radioactive elements have a significant effect on performance even at low concentrations, so it is required to reduce the amount of silica powder mixed in, but uranium and the like are contained in the natural world in relatively large amounts. Even the abundance can affect performance.

  Therefore, conventionally, the content of uranium has been reduced for the members constituting the pulverizer for pulverizing the quartzite. However, the members constituting the pulverizer are complicated in separating uranium such as metal and ceramics from the viewpoint of durability. It is often composed of materials, and a great deal of labor is required to remove uranium, which contributes to an increase in the cost of manufactured silica powder.

  The present invention has been completed in view of the above circumstances, and a method for producing spherical silica powder capable of producing silica powder at a low cost, and a semiconductor sealing material using the spherical silica powder produced by the production method Providing a manufacturing method is a problem to be solved.

  As a result of intensive studies conducted by the present inventors for the purpose of solving the above problems, the following invention has been completed. That is, the method for producing the spherical silica powder of the present invention includes a pulverization step in which crushed silica stones having a uranium content of a predetermined value (for example, 1 ppb) or less collide with each other in a high-speed fluid to be pulverized into a pulverized product, And a melt spheronization step in which the pulverized product is put into a flame and melt spheroidized.

  That is, it is possible to effectively prevent uranium from being mixed from the pulverizer by adopting a method capable of performing the pulverization operation without contacting the pulverizer as much as possible.

  In particular, the pulverization step is preferably performed in a pulverization vessel lined with a polymer material. Even in the pulverizing apparatus that realizes the manufacturing method of the present invention, the silica powder riding on the high-speed fluid may collide with the wall of the container that performs the pulverizing operation in the pulverizing apparatus, so that the material constituting the container wall may be mixed. However, mixing of uranium can be effectively prevented by grinding in a container coated with a polymer material.

  Here, since it is relatively easy to remove uranium from the polymer material, uranium can be prevented from being mixed even if the polymer material is mixed. Furthermore, even if the polymer material is mixed in the pulverized product, the polymer material can be oxidized and scattered in the subsequent melt spheronization step, and therefore, there is an advantage that it does not become a problem. By adopting an elastomer as the polymer material, it becomes difficult to be scraped off, and impurities can be prevented from being mixed into the pulverized product.

  And the semiconductor sealing material of this invention which solves the said subject has the process of disperse | distributing the spherical silica powder manufactured by the manufacturing method of the spherical silica powder mentioned above in the resin composition for dispersion | distribution, It is characterized by the above-mentioned. To do.

  By adopting the method for producing the spherical silica powder of the present invention that can reduce uranium contamination, uranium contamination can also be prevented for the semiconductor sealing material.

  The method for producing the spherical silica powder of the present invention has an advantage that the spherical silica powder can be produced at a low cost because it can easily prevent uranium from being mixed.

  The manufacturing method of the spherical silica powder of this embodiment is a method of manufacturing the spherical silica powder by a so-called flame melting method. Since the spherical silica powder produced by the production method of the present embodiment has little uranium contamination, it is difficult to cause soft errors due to emission of uranium-derived α rays even when used as a filler for semiconductor encapsulants. is there.

  Moreover, the spherical silica powder manufactured by this manufacturing method can prepare a resin composition by disperse | distributing and adding in resin. This resin composition can be used as a sealing material for semiconductor elements, and can also be used for substrate materials, inorganic pastes, adhesives, coating agents, precision molding resins, prepregs, and the like.

  The method for producing spherical silica powder of the present embodiment includes a pulverization step and a melt spheronization step.

  The pulverization step is a step of obtaining a pulverized product of silica having a size suitable as a raw material for the spherical silica powder to be finally produced by pulverizing the crushed product of silica. Quartzite crushed material is obtained by crushing quartzite. Although it does not specifically limit as a property of a crushed silica stone, It is desirable that a particle size is about 0.1-1.0 mm.

  Although there is a possibility that uranium derived from the crushing apparatus may be mixed in the crushing process here, since the surface area per unit mass is small at the stage of the crushed material, the mixing of uranium is rarely a problem.

  However, it is desirable to reduce the uranium content of the member in contact with the crushed material in the crushing device for the purpose of suppressing uranium contamination during crushing. Although the production cost of the spherical silica powder increases by controlling the uranium content in the crushing device, it can be assumed that the amount of material derived from the crushing device at the time of crushing is small, so the uranium content in the crushing device described later It is possible to suppress an increase in cost rather than controlling.

  The silica is an ore containing silicic acid anhydride as a main component, and a material having a uranium content of a predetermined value or less is used. The predetermined value is a value that can be set according to the use of the finally produced spherical silica powder, and can be set to about 1 ppb when used for a semiconductor sealing material such as a memory element. The method for controlling the uranium content contained in the silica is not particularly limited. The formation of the uranium content within the predetermined value can be used from the beginning, or the uranium content can be controlled by some technique. Examples of quartzite include quartz, white quartzite, blue-white quartzite, red-white quartzite, soft quartzite, quartz sand, etc., and select the appropriate impurity concentration, availability, and price. .

  The pulverization step is a step in which crushed silica stones are crushed by colliding with each other in a high-speed fluid. Specifically, it is a method of pulverizing by colliding the crushed silica stones with a carrier gas such as air or nitrogen gas by pressurizing them, and is generally called a jet mill. Device included.

  In particular, the pulverization can be efficiently performed by performing pulverization using two or more pressure nozzles arranged so as to collide with each other. The crushed quartzite crushed material is pulverized to a predetermined particle size, which is a required particle size, by being repeatedly injected with high pressure. An example of the predetermined particle size is about 0.1 μm to 50 μm in the case of producing spherical silica powder applied to a general semiconductor sealing material.

  For the purpose of separating the pulverized product having a predetermined particle size or less, it is possible to incorporate a classification means and perform the classification operation together with the pulverization operation. Further, the pulverization operation can be similarly performed by using a liquid such as water as the fluid, and dispersing the crushed silica in the liquid and performing high-pressure injection.

  The high-speed fluid is usually ejected in some kind of container (pulverization container). It is desirable to use a container lined with a polymer material as the pulverization container. The polymer material to be lined is not particularly limited, but it is desirable to employ an elastomer. As the elastomer, any of natural rubber and synthetic rubber (polybutadiene rubber, butadiene-acrylonitrile rubber, chloroprene rubber, etc.) can be employed. Even rubber that has not been vulcanized at all can be employed. Other polymer materials that can be used include polyolefins (polyethylene (high density, low density), polypropylene, polytetrafluoroethylene, ETFE, PVDF, polyamide, polyester, polyurethane, silicone, etc.) Examples of desirable materials for the molecular material include polyurethane and silicone.

  The melt spheronization step is a step in which the pulverized product obtained in the pulverization step is melted to obtain a spheroidized silica powder. Specifically, spherical silica fine particles are produced by charging and melting a pulverized product in a flame and then cooling and solidifying it.

  Melting and solidification is performed in a furnace composed of refractory bricks, etc., but in order to prevent impurities from being mixed, materials with low impurity content are used for the parts that come into contact with silica raw materials such as refractory bricks. It is desirable to do.

  The manufacturing method of the semiconductor sealing material of this embodiment has the process of disperse | distributing the spherical silica powder obtained by the manufacturing method of the above-mentioned this embodiment in the resin composition for dispersion | distribution. The spherical silica powder is desirably contained in an amount of 85% by mass or more based on the total mass.

  The resin composition for dispersion is not particularly limited, but it is desirable to employ a thermosetting resin (or a precursor thereof). For example, a cationic polymerizable compound can be employed. Examples of the cationic polymerizable compound include epoxy resins, oxirane resins, oxetane compounds, cyclic ether compounds, cyclic lactone compounds, thiirane compounds, cyclic acetal compounds, cyclic thioether compounds, spiro orthoester compounds, vinyl compounds, and the like. Can be used alone or in combination.

  In particular, an epoxy resin is preferable from the viewpoints of availability, handleability, and the like. Although an epoxy resin is not specifically limited, The monomer, oligomer, and polymer which have two or more epoxy groups in 1 molecule are mentioned. For example, biphenyl type epoxy resin, stilbene type epoxy resin, bisphenol type epoxy resin, triphenol methane type epoxy resin, alkyl modified triphenol methane type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, naphthol type epoxy resin, triazine core containing An epoxy resin is mentioned.

  Specific examples other than the epoxy resin include oxirane compounds such as phenylglycidyl ether, ethylene oxide and epichlorohydrin; oxetane compounds such as trimethylene oxide, 3,3-dimethyloxetane and 3,3-dichloromethyloxetane; tetrahydrofuran, 2 Cyclic ether compounds such as 1,3-dimethyltetrahydrofuran, trioxane, 1,3-dioxofuran, 1,3,6-trioxacyclooctane; cyclic lactone compounds such as β-propiolactone and ε-caprolactone; ethylene sulfide, 3, Thiane compounds such as 3-dimethylthiirane; Thiane compounds such as 1,3-propyne sulfide and 3,3-dimethyl thietane; Cyclic thioether compounds such as tetrahydrothiophene derivatives; Spiro ortho ester compounds obtained by reaction with kuton; spiro ortho carbonate compounds; cyclic carbonate compounds; vinyl compounds such as ethylene glycol divinyl ether, alkyl vinyl ether, triethylene glycol divinyl ether; styrene, vinyl cyclohexene, isobutylene, polybutadiene, etc. An ethylenically unsaturated compound can be illustrated. As a cationically polymerizable compound, an epoxy resin and these compounds can be used alone or in combination.

  Further, a curing agent and a curing catalyst can be mixed in order to cure the cationic polymerizable compound. As the curing agent, primary amine, secondary amine, phenol resin, and acid anhydride can be used. As the curing catalyst, a phosphorus-based imidazole compound, a tertiary amine, or the like is used. In addition, a Lewis acid can be complexed with a tertiary amine, an onium salt, or the like and used as a latent heating catalyst. Specific examples of the curing agent include diaminodiphenylmethane, hexahydrophthalic anhydride, and phenol resin (novolak). Examples of the curing catalyst include 2-methylimidazole, triphenylphosphine, and 1,8-diazabicycloundecene.

Example: 100 kg of crushed quartzite (quartz sand: volume average particle size of about 1 mm) with a uranium concentration of 0.3 ppb was pulverized with a jet mill (Nihon Pneumatic Kogyo, PJM-200SP) at a processing rate of 20 kg / hour. (Grinding step). The pulverization condition was an air pressure of 0.6 MPa. The jet mill used a device equipped with a cyclone dust collector and a bag filter in the rear. Furthermore, the inside of the pulverizing container was lined with natural rubber.

  After the pulverization, the silica powder was recovered as a pulverized product with a cyclone dust collector. A silica powder having a volume average particle diameter of 5 μm was obtained with a recovery rate of 60%. The uranium concentration in the obtained silica powder was 0.5 ppb.

And LPG gas supplied at 5 Nm ³ / time in the furnace is a refractory material tension has been furnace (cylindrical height 5 m × inside diameter 0.5 m), to supply and burning an oxygen gas supplied at 25 Nm ³ / time The silica powder obtained in the course of generating the flame was dispersed into the air stream at a rate of 10 kg / hour, heated and melted, and then recovered to obtain a spheroidized silica powder having a volume average particle diameter of 7 μm ( Melt spheronization step). The uranium concentration in the obtained spherical silica powder was 0.6 ppb.
Comparative Example: 100 kg of the same quartz sand as in the example was pulverized with a 300 L ball mill (manufactured by Chuo Kakoki, model number: MB-300) at a processing rate of 20 kg / hour. After pulverization, a silica powder having a volume average particle size of 5 μm was obtained. The uranium concentration in the obtained silica powder was 100 ppb.

A step corresponding to the melt spheronization step was performed in the same manner as in the example. After melting by heating, recovery was performed to obtain a spheroidized silica powder having a volume average particle diameter of 7 μm. The uranium concentration in the obtained spherical silica powder was 100 ppb.
As is apparent from the above results, the spherical silica powder prepared by the manufacturing method of this example can keep the uranium concentration lower than the spherical silica powder prepared by the manufacturing method of the comparative example. It was. This is considered to be due to the fact that it was possible to effectively prevent contamination of wear-derived impurities from the pulverizer.

Claims (5)

A pulverization step in which crushed silica stones having a uranium content of a predetermined value or less collide with each other in a high-speed fluid to be pulverized into a pulverized product,
A melt spheronization step in which the pulverized product is put into a flame and melt spheroidized;
A method for producing a spherical silica powder, comprising:   The method for producing a spherical silica powder according to claim 1, wherein the predetermined value is 1 ppb.   The method for producing spherical silica powder according to claim 1 or 2, wherein the pulverization step is performed in a pulverization container lined with a polymer material.   The method for producing spherical silica powder according to claim 3, wherein the polymer material is an elastomer.   The manufacturing method of the semiconductor sealing material which has the process of disperse | distributing the spherical silica powder manufactured with the manufacturing method of the spherical silica powder in any one of Claims 1-4 in the resin composition for dispersion | distribution.