Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B21/00—Nitrogen; Compounds thereof
  • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
  • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/38—Boron-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W40/00—Arrangements for thermal protection or thermal control
  • H10W40/20—Arrangements for cooling
  • H10W40/25—Arrangements for cooling characterised by their materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W74/00—Encapsulations, e.g. protective coatings
  • H10W74/40—Encapsulations, e.g. protective coatings characterised by their materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W74/00—Encapsulations, e.g. protective coatings
  • H10W74/40—Encapsulations, e.g. protective coatings characterised by their materials
  • H10W74/43—Encapsulations, e.g. protective coatings characterised by their materials comprising oxides, nitrides or carbides, e.g. ceramics or glasses
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/50—Agglomerated particles
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• the present disclosure relates to a method for producing boron nitride powder, boron nitride powder, and a resin sealing material.
• Boron nitride powder which is an aggregate of boron nitride particles, has lubricating properties, high thermal conductivity, insulating properties, etc., and is widely used for applications such as solid lubricants, thermally conductive fillers, and insulating fillers. .
• Boron nitride particles especially hexagonal boron nitride particles
• a resin sealing material for a semiconductor memory element needs to be made of a material that hardly emits ⁇ -rays so as not to cause soft errors in the semiconductor memory element. As such a material, it is particularly desirable to use a material with a low uranium content.
• aggregated particles as disclosed in Patent Document 1 usually contain a small amount of uranium. Also, due to its structure, the uranium trapped inside the agglomerated particles is difficult to remove. Therefore, it is difficult to reduce the uranium content in agglomerated particles after they are formed.
• the present disclosure provides at least [1] to [9] below.
• a preparatory step of preparing the boron carbonitride powder is further included, wherein the preparatory step is an acid treatment step of contacting the boron carbide powder with an acid solution containing hydrofluoric acid to acid-treat the boron carbide powder. and a pressurized nitriding step of firing the acid-treated boron carbide powder in a pressurized nitrogen atmosphere.
• the treatment temperature in the acid treatment step is 60°C or higher, the treatment time in the acid treatment step is 3 hours or longer, and the acid concentration of the acid solution is 20% by mass or higher, [4] or [ 5], the method for producing a boron nitride powder.
• a boron nitride powder containing agglomerated particles composed of agglomerated primary particles of boron nitride, having an orientation index of 15 or less and a uranium content of 20 mass ppb or less.
• a resin sealing material for a semiconductor memory device containing the boron nitride powder according to [7] or [8].
• a method for producing a boron nitride powder containing agglomerated particles composed of agglomerated primary particles of boron nitride and having a reduced uranium content can.
• a boron nitride powder containing agglomerated particles composed of agglomerated primary particles of boron nitride and having a sufficiently low uranium content it is possible to provide a resin encapsulant for a semiconductor memory device containing the boron nitride powder of the aspect described above.
• each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. .
• a numerical range indicated using “to” indicates a range including the numerical values before and after "to” as the minimum and maximum values, respectively. Also, unless otherwise specified, the units of numerical values described before and after "-" are the same.
• the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples. Moreover, the upper limit value and the lower limit value described individually can be combined arbitrarily.
• a method for producing a boron nitride powder includes firing a raw material mixture containing a boron carbonitride powder, a boron source, and a carbonate to produce primary particles of boron nitride, and the primary particles are aggregated. including a decarburizing crystallization step to obtain a powder comprising aggregated particles that are structured.
• the method for producing boron nitride powder may further include a preparation step of preparing the boron carbonitride powder used in the decarburization and crystallization step.
• the preparatory step includes, for example, a pressurized nitriding step of firing the boron carbide powder in a pressurized nitrogen atmosphere.
• the preparation step may further include an acid treatment step (first acid treatment step) of acid-treating the boron carbide powder by contacting the boron carbide powder with an acid solution containing hydrofluoric acid.
• the pressurized nitriding step uses acid-treated boron carbide powder obtained through the acid treatment step.
• the preparation step may further include an acid treatment step (second acid treatment step) of acid-treating the boron carbonitride powder by contacting the boron carbonitride powder with an acid solution containing hydrofluoric acid.
• the boron carbonitride powder used in the second acid treatment step may be a powder obtained through a pressure nitriding step.
• the preparation step includes the second acid treatment step, the acid-treated boron carbonitride powder obtained through the acid treatment step is used in the decarburization and crystallization step.
• the amounts of the boron source and the carbonate used in the decarburization and crystallization step are set within the predetermined ranges, respectively, and then the first acid treatment step and/or the second acid treatment step are performed to finally obtain The uranium content in the boron nitride powder obtained in 1 can be further reduced.
• the boron carbide powder (B 4 C powder) is brought into contact with an acid solution containing hydrofluoric acid, thereby dissolving the portions of the boron carbide particles that come into contact with the acid solution. This removes at least part of the uranium present in the boron carbide powder (in particular, uranium present near the surface of the boron carbide particles).
• Boron carbide powder is an aggregate of boron carbide particles.
• the purity of the boron carbide powder (content of boron carbide) is preferably, for example, 97% by mass or more.
• As the boron carbide powder commercially available boron carbide powder may be used, or separately prepared boron carbide powder may be used.
• Boron carbide powder for example, after mixing boric acid and acetylene black, is heated in an inert gas atmosphere at 1800 to 2400 ° C. for 1 to 10 hours to obtain a boron carbide mass;
• a boron lump can be obtained by a method including steps of pulverizing, sieving, washing, removing impurities, drying, etc. as appropriate to prepare a boron carbide powder.
• boron carbide powder As the boron carbide powder, it is preferable to use boron carbide powder having an average particle size of 10 ⁇ m or more (for example, 10 to 50 ⁇ m) from the viewpoint of improving the removal efficiency of uranium during acid treatment. From the same point of view, it is preferable to use boron carbide powder having a specific surface area of 1 m 2 /g or less (for example, 0.05 to 1 m 2 /g).
• the acid solution is an aqueous solution containing hydrofluoric acid as an acid component.
• An aqueous solution of hydrogen fluoride is sometimes referred to as hydrofluoric acid, but in this specification, among the acid components contained in the aqueous solution (acid solution), a compound represented by HF is referred to as hydrofluoric acid.
• an acid component is defined as a substance that dissolves in water and releases hydrogen ions.
• the concentration of hydrofluoric acid in the acid solution may be 0.1% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, or 10% by mass. % or more.
• the concentration of hydrofluoric acid in the acid solution may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 30% by mass or less from the viewpoint of production cost and safety. From these points of view, the concentration of hydrofluoric acid in the acid solution is, for example, 0.1 to 50% by mass, 1 to 50% by mass, 2 to 45% by mass, 3 to 40% by mass, or 10 to 30% by mass.
• the concentration of hydrofluoric acid means the content of hydrofluoric acid (HF) based on the total mass of the acid solution.
• the acid solution may be a mixed acid that further contains an acid component other than hydrofluoric acid.
• the ratio of hydrofluoric acid to all acid components in the acid solution may be 4% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, from the viewpoint of improving the uranium removal efficiency. It may be at least 40% by mass or at least 40% by mass.
• the proportion of hydrofluoric acid in all acid components may be 80% by mass or less, 70% by mass or less, or 60% by mass or less from the viewpoint of production cost and safety. From these viewpoints, the proportion of hydrofluoric acid in the total acid component is, for example, 4 to 80% by mass, 10 to 70% by mass, 20 to 60% by mass, 30 to 60% by mass, or 40 to 60% by mass. It's okay.
• Acid components other than hydrofluoric acid that can be contained in the acid solution include, for example, hydrochloric acid (HCl), nitric acid (HNO 3 ), sulfuric acid (HSO 4 ), and the like.
• hydrochloric acid is preferably used from the viewpoint of improving the removal efficiency of uranium.
• the concentration of hydrochloric acid in the acid solution may be 2% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, and 20% by mass. Above, it may be 30% by mass or more, or 40% by mass or more. From the viewpoint of production cost and safety, the concentration of hydrochloric acid in the acid solution may be 60% by mass or less, 50% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less. good.
• the concentration of hydrochloric acid in the acid solution is, for example, 2 to 60% by mass, 3 to 60% by mass, 5 to 60% by mass, 7 to 60% by mass, 10 to 60% by mass, 20 to 60% by mass. %, 30-60% by weight or 40-60% by weight, and may be 5-35% by weight, 7-30% by weight or 10-25% by weight.
• the concentration of hydrochloric acid means the content of hydrochloric acid (HCl) based on the total mass of the acid solution.
• the acid concentration of the acid solution may be 2% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more. Alternatively, it may be 40% by mass or more.
• the acid concentration of the acid solution may be 50% by mass or less, 45% by mass or less, or 40% by mass or less from the viewpoint of production cost and safety. From these viewpoints, the acid concentration of the acid solution is, for example, 2 to 50% by mass, 3 to 45% by mass, 5 to 40% by mass, 10 to 50% by mass, 20 to 50% by mass, 30 to 50% by mass, or It may be 40 to 50% by mass.
• the acid concentration means the content of all acid components based on the total mass of the acid solution.
• the method of contacting the boron carbide powder with the acid solution is not particularly limited, but for example, a method of mixing the boron carbide powder and the acid solution by putting the boron carbide powder into the acid solution, or a method of mixing the boron carbide powder with the acid solution. and a method of continuously injecting.
• the mixed liquid containing the boron carbide powder and the acid solution may be stirred from the viewpoint of improving the uranium removal efficiency. Stirring can be performed using, for example, a stirrer, magnetic stirrer, disperser, or the like.
• the acid treatment of the boron carbide powder may be repeated multiple times. For example, a series of operations of mixing boron carbide powder and an acid solution, separating the boron carbide powder from the acid solution after a certain period of time has passed, and mixing the separated boron carbide powder again with a new acid solution is repeated.
• the amount of the acid solution used may be, for example, 80 parts by mass or more, 500 parts by mass or less, or 80 to 500 parts by mass with respect to 100 parts by mass of the boron carbide powder.
• the treatment temperature in the acid treatment step may be 40°C or higher, 60°C or higher, or 75°C or higher from the viewpoint of improving the uranium removal efficiency.
• the treatment temperature in the acid treatment step may be 95° C. or lower, 92° C. or lower, or 90° C. or lower from the viewpoint of suppressing deterioration in treatment efficiency due to volatilization of hydrogen fluoride and from the viewpoint of safety. From these points of view, the treatment temperature in the acid treatment step may be, for example, 40-95°C, 60-92°C or 75-90°C.
• the above treatment temperature indicates the temperature of the acid solution that is brought into contact with the boron carbide powder during the acid treatment. When the boron carbide powder is acid-treated by mixing the boron carbide powder and the acid solution, the treatment temperature can be said to be the temperature of the mixed liquid containing the boron carbide powder and the acid solution.
• the treatment time in the acid treatment step may be 1 hour or more, 2 hours or more, 3 hours or more, or 5 hours or more.
• the treatment time in the acid treatment step may be 15 hours or less, 12 hours or less, or 10 hours or less from the viewpoint of production cost and safety. From these points of view, the treatment time in the acid treatment step may be, for example, 1 to 15 hours, 2 to 12 hours, 3 to 10 hours, or 5 to 10 hours.
• the above treatment time indicates the contact time between the boron carbide powder and the acid solution.
• the treatment temperature in the acid treatment step is 60° C. or higher and the treatment time in the acid treatment step is 3 hours or longer, and the treatment temperature in the acid treatment step is 60° C. or higher. More preferably, the treatment time in the acid treatment step is 3 hours or more, and the acid concentration of the acid solution is 20% by mass or more.
• the boron carbide powder is sintered in a pressurized nitrogen atmosphere to nitride the boron carbide and obtain a sintered product containing boron carbonitride.
• the resulting fired product tends to contain hexagonal boron carbonitride with high purity.
• the boron carbide powder include those exemplified as the boron carbide powder used in the first acid treatment step.
• acid-treated boron carbide powder obtained through the first acid treatment step is used.
• the firing temperature in the pressurized nitriding step is preferably higher than the firing temperature in the decarburization and crystallization step.
• the firing temperature in the pressurized nitriding step may be, for example, 1900-2200°C, 2000-2200°C or 2100-2200°C. By setting the firing temperature within the above range, the crystallinity of the boron carbonitride can be enhanced and the proportion of hexagonal boron carbonitride can be increased.
• the baking time in the pressurized nitriding step is not particularly limited as long as the nitriding is sufficiently progressed, and may be, for example, 6 to 30 hours, 8 to 25 hours, or 10 to 20 hours.
• the pressure (atmospheric pressure) in the pressurized nitriding step may be, for example, 0.6 to 1 MPa, 0.7 to 1 MPa, or 0.8 to 1 MPa.
• the pressure indicates a gauge pressure.
• the nitrogen gas concentration of the nitrogen pressurized atmosphere in the pressurized nitriding step may be, for example, 95% by volume or more, 98% by volume or more, or 99.9% by volume or more.
• the upper limit of the nitrogen gas concentration is 100% by volume.
• the fired product obtained in the pressurized nitriding step may be used as it is in the decarburization and crystallization step, and may be subjected to pulverization treatment, classification treatment, washing treatment, heat treatment (for example, oxidation treatment in an atmosphere containing oxygen), etc. as appropriate. It may be used in the decarburization and crystallization step after being carried out.
• the pulverization treatment can be performed using a general pulverizer or pulverizer such as a ball mill, vibration mill, or jet mill.
• "pulverization" in this specification also includes "crushing".
• Decarburization crystallization step In the decarburization and crystallization step, the boron carbonitride powder (B 4 CN 4 powder) is fired together with a boron source and a carbonate, thereby decarburizing the boron carbonitride and increasing the crystallinity of the boron nitride. . As a result, a boron nitride powder (BN powder) containing agglomerated particles in which primary particles of boron nitride are agglomerated is obtained.
• BN powder boron nitride powder
• the boron nitride in the boron nitride powder obtained by this method is usually hexagonal boron nitride, and contains aggregated particles in which primary particles of scale-like hexagonal boron nitride are aggregated.
• Boron carbonitride powder is an aggregate of boron carbonitride particles.
• the purity of the boron carbonitride powder (content of boron carbonitride) is preferably 98% by mass or more, for example.
• a commercially available boron carbonitride powder may be used, or the powder prepared in the above preparation step may be used. From the viewpoint of increasing the ratio of hexagonal boron nitride in the obtained boron nitride powder, it is preferable to use a boron carbonitride powder having a high ratio of hexagonal boron carbonitride, and the boron carbonitride powder obtained through the above pressure nitriding step. is more preferred.
• Boron sources include, for example, boric acid and boron oxide. These can be used individually by 1 type or in combination of 2 or more types.
• boric acid is preferably used from the viewpoint of easily obtaining the effect of promoting the growth of primary particles and from the viewpoint of easily reducing the uranium content.
• Carbonates include, for example, sodium carbonate, calcium carbonate, strontium carbonate, and the like. These can be used individually by 1 type or in combination of 2 or more types.
• sodium carbonate is preferably used from the viewpoint of easily obtaining the effect of promoting the growth of primary particles and from the viewpoint of easily reducing the uranium content.
• the amount of the boron source used may be 55% by mass or more, 57% by mass or more, or 59% by mass or more.
• the amount of the boron source used may be 70% by mass or less, 65% by mass or less, or 60% by mass or less from the viewpoint of increasing the crushing strength of the aggregated particles.
• the amount of boron source used may be less than 55% by weight.
• the amount of the boron source used is 50% by mass or more, the growth of the primary particles of boronitride is likely to be promoted, and the boron nitride powder having an average particle size of 10 to 90 ⁇ m and a crushing strength of 5 MPa or more. becomes easier to obtain.
• the amount of the boron source used is 50 to 70% by mass, 55 to 70% by mass, 57 to 70% by mass, 59 to 70% by mass, 55 to 65% by mass, 57 to 65% by mass, 59 to 65% by mass. % by weight, 55-60% by weight, 57-60% by weight or 59-60% by weight.
• the amount used is the amount based on the total mass of the raw material mixture, but the amount used based on the total amount of the boron carbonitride powder, the boron source and the carbonate may be within the above range. .
• the amount of carbonate used may be 4% by mass or more, 5% by mass or more, or 6% by mass or more.
• the amount of carbonate used may be 10% by mass or less, 8% by mass or less, or 6% by mass or less from the viewpoint of increasing the crushing strength of aggregated particles.
• the amount of carbonate used may be less than 4% by mass.
• the amount of carbonate used is 1% by mass or more, the growth of primary particles of boron nitride is likely to be promoted, and the boron nitride powder having an average particle size of 10 to 90 ⁇ m and a crushing strength of 5 MPa or more. becomes easier to obtain.
• the amount of carbonate used is 1 to 10% by mass, 4 to 10% by mass, 5 to 10% by mass, 6 to 10% by mass, 4 to 8% by mass, 5 to 8% by mass, 6 to 8% by mass. % by weight, 4-6% by weight or 5-6% by weight.
• the amount used is the amount based on the total mass of the raw material mixture, but the amount used based on the total amount of the boron carbonitride powder, the boron source and the carbonate may be within the above range. .
• materials other than the boron carbonitride powder, the boron source and the carbonate may be used, or only the boron carbonitride powder, the boron source and the carbonate may be used.
• the firing temperature in the decarburization and crystallization step is preferably 1800°C or higher, and may be 1900°C or higher or 2000°C or higher. By setting the sintering temperature to 1800° C. or higher, the primary particles can be grown more sufficiently.
• the firing temperature in the decarburization and crystallization step is preferably 2400° C. or lower, and may be 2200° C. or lower or 2100° C. or lower. By setting the firing temperature to 2400° C. or lower, yellowing of the boron nitride powder can be suppressed. From the above point of view, the firing temperature in the decarburization and crystallization step may be, for example, 1800-2400°C, 1900-2200°C or 2000-2100°C.
• the said baking temperature means the holding temperature during heating (baking).
• the heating start temperature is not particularly limited, but may be room temperature (for example, 25°C).
• the temperature increase rate up to 1000° C. may be, for example, 1 to 10° C./min, and the temperature increase rate at 1000° C. or higher may be, for example, 0.1 to 10° C./min. It may be 5°C/min.
• the firing time in the decarburization and crystallization step is preferably 4 hours or longer, and may be 6 hours or longer or 8 hours or longer. By setting the firing time to 4 hours or longer, the growth of the primary particles can be sufficiently advanced.
• the firing time in the decarburization and crystallization step is preferably 40 hours or less, and may be 30 hours or less or 20 hours or less. By setting the firing time to 40 hours or less, it is possible to suppress an increase in manufacturing cost. From the above point of view, the firing time in the decarburization and crystallization step may be, for example, 4 to 40 hours, 6 to 30 hours, or 8 to 20 hours.
• the firing time means the retention time at the firing temperature (holding temperature).
• the uranium content can also be reduced by changing the firing conditions in the decarburization and crystallization process.
• the firing temperature is 1800° C. or more and the firing time is 8 hours or more, or the firing temperature is 2000° C. or more and the firing time is 4 hours or more. More preferably, the firing temperature is 2000° C. or higher, and the firing time is 8 hours or longer.
• the firing atmosphere in the decarburization and crystallization step may be, for example, air or vacuum, or may be an inert gas atmosphere such as nitrogen gas or argon gas.
• the calcination in the decarburization and crystallization step may be performed under normal pressure (atmospheric pressure) or under atmospheric pressure or higher.
• the pressure (atmospheric pressure) in the decarburization and crystallization step may be, for example, 10 kPa or more, 15 kPa or more, or 20 kPa or more.
• the pressure (atmospheric pressure) in the decarburization and crystallization step may be, for example, 80 kPa or less, 60 kPa or less, or 40 kPa or less. By setting the pressure to 80 kPa or less, it is possible to further suppress the collapse of the aggregated particles during the decarburization and crystallization step.
• the pressure (atmospheric pressure) in the decarburization and crystallization step may be 10 to 80 kPa, 10 to 60 kPa, or 20 to 40 kPa. Note that the above pressure indicates a gauge pressure.
• the boron nitride powder after the decarburization and crystallization process may be appropriately subjected to pulverization treatment, classification treatment, washing treatment, and the like.
• the pulverization treatment can be performed using a general pulverizer or pulverizer such as a ball mill, vibration mill, or jet mill.
• boron nitride powder having an orientation index of 15 or less, including aggregated particles composed of agglomerated primary particles of boron nitride.
• the amount of the boron source and the carbonate used in the decarburization and crystallization step is set to 55% by mass or more and 4% by mass or more, respectively, and an acid containing hydrofluoric acid
• the uranium content can be reduced while forming agglomerated particles composed of agglomerated primary particles of boron nitride. It is not necessary to implement all of these means for reducing the uranium content, but by combining a plurality of means, it is possible to provide a boron nitride powder with a further reduced uranium content.
• the orientation index of boron nitride powder means a value measured according to the following method.
• the X-ray diffraction spectrum of the boron nitride powder is obtained, and from the X-ray diffraction spectrum, the peak intensity I (002) corresponding to the (002) plane and the (100) plane and I(100).
• the obtained peak intensity is used to calculate the orientation index [I(002)/I(100)] of the boron nitride powder.
• the X-ray diffractometer for example, "ULTIMA-IV" (product name) manufactured by Rigaku Corporation is used.
• a boron nitride powder includes agglomerated particles composed of agglomerated primary particles of boron nitride, has an orientation index of 15 or less, and has a uranium content of 20 mass ppb or less.
• the boron nitride powder may contain primary particles in addition to aggregated particles.
• the primary particles of boron nitride may be, for example, scale-like hexagonal boron nitride particles.
• the boron nitride powder Since the boron nitride powder has a uranium content of 20 mass ppb or less, it can be said that it is a material that hardly emits ⁇ -rays. In addition, since the boron nitride powder has an orientation index of 15 or less, according to the boron nitride powder, when at least a part of the aggregated particles collapses during kneading with the resin, and the orientation increases Even so, it is possible to suppress occurrence of large anisotropy in the heat dissipation property and the like of the resin sealing material. Therefore, the boron nitride powder is suitable for use as a resin encapsulant for semiconductor memory devices, which require heat dissipation.
• the boron nitride powder can be obtained, for example, in the manufacturing method according to the above embodiment, by setting the amount of the boron source and the carbonate used in the decarburization and crystallization step to 55% by mass or more and 4% by mass or more, respectively. can.
• the uranium content of the boron nitride powder may be, for example, 18 mass ppb or less, 16 mass ppb or less, 14 mass ppb or less, 12 mass ppb or less, 10 mass ppb or less, 7 mass ppb or less, or 5 mass ppb or less.
• Boron nitride powder having such a uranium content is obtained by, for example, acid treatment, in addition to using amounts of boron source and carbonate of 55% by mass or more and 4% by mass or more, respectively, in the decarburization and crystallization step.
• the lower limit of the uranium content may be, for example, 5 mass ppb.
• the uranium content is, for example, 5-20 mass ppb, 5-18 mass ppb, 5-16 mass ppb, 5-14 mass ppb, 5-12 mass ppb, 5-10 mass ppb or 5-7 mass ppb. you can The above content is based on the total mass of the boron nitride powder.
• the uranium content of boron nitride powder in this specification means a value measured according to the following method.
• JCRS108 boron nitride powder chemical analysis method 0.5 g of a sample (boron nitride powder) is subjected to pressure acid decomposition in a mixed solution of nitric acid, sulfuric acid and hydrofluoric acid at 180° C. for 18 hours. Thereafter, the solution obtained by pressure acid decomposition is dried on a hot plate to solidify, and the obtained solid content is mixed with nitric acid to obtain a mixed solution.
• ICP-MS inductively coupled plasma mass spectrometer
• the orientation index may be 12 or less or 10 or less from the viewpoint of further reducing the influence of the collapse of the aggregated particles.
• the orientation index may be 3 or higher, 4 or higher, or 6 or higher, and may be 3-15, 4-12, or 6-10.
• the orientation index of the boron nitride powder can be adjusted, for example, by controlling the growth of primary particles when producing the boron nitride powder.
• the purity of the boron nitride powder is preferably 98.5% by mass or higher, and may be 99% by mass or higher or 99.5% by mass or higher.
• the upper limit of the purity of the boron nitride powder is not particularly limited, and may be 100% by mass or 99.5% by mass.
• the purity of boron nitride powder herein means a value determined by titration, which will be described later.
• a sample of boron nitride powder is alkali-decomposed with sodium hydroxide, ammonia is distilled from the decomposed solution by a steam distillation method, and collected in an aqueous boric acid solution. This collected liquid is titrated with a normal sulfuric acid solution.
• the content of nitrogen atoms (N) in the sample is calculated from the titration results. From the obtained nitrogen atom content, the boron nitride content in the sample can be determined based on formula (I), and the purity of the boron nitride powder can be calculated.
• the formula weight of boron nitride is 24.818 g/mol, and the atomic weight of nitrogen atoms is 14.006 g/mol.
• Boron nitride content [mass%] in the sample nitrogen atom (N) content [mass%] x 1.772 (I)
• the aggregated particles contained in the boron nitride powder preferably have a crushing strength of 5 MPa or more from the viewpoint of being difficult to collapse when kneading with the resin.
• the crushing strength of the aggregated particles may be 8 MPa or more, or 10 MPa or more.
• the crush strength of the agglomerated particles may be 20 MPa or less, 15 MPa or less, or 12 MPa or less.
• the crushing strength of the aggregated particles is 20 Mpa or less, at least a part of the aggregated particles appropriately collapses during kneading with the resin, and the generation of voids is easily suppressed. As a result, the resulting resin encapsulant has higher insulation.
• the crushing strength of the aggregated particles may be, for example, 5-20 MPa, 8-15 MPa or 10-12 MPa.
• the crushing strength of aggregated particles can be adjusted, for example, by changing the firing conditions.
• the crushing strength herein is a value measured in accordance with the description of JIS R 1639-5:2007 "Fine ceramics-Method for measuring (granule) properties-Part 5: Single granule crushing strength”.
• the measurement was performed on 20 or more aggregated particles, and the value at the time when the cumulative destruction rate was 63.2% was calculated.
• a microcompression tester can be used for the measurement.
• As the microcompression tester for example, "MCT-W500" (product name) manufactured by Shimadzu Corporation can be used.
• the average particle size of the boron nitride powder may be, for example, 90 ⁇ m or less, 80 ⁇ m or less, or 70 ⁇ m or less. When the average particle diameter is 90 ⁇ m or less, it becomes possible to make the sealing portion formed by the resin sealing material thinner.
• the average particle size of the boron nitride powder may be, for example, 10 ⁇ m or more, 20 ⁇ m or more, or 30 ⁇ m or more. When the average particle diameter is 10 ⁇ m or more, the thermal conductivity of the resin sealing material can be further improved. From these points of view, the average particle size of the boron nitride powder may be, for example, 10-90 ⁇ m, 20-80 ⁇ m, or 30-70 ⁇ m.
• the average particle diameter in this specification means the 50% cumulative diameter (median diameter) in the volume-based cumulative particle size distribution. More specifically, it means the particle diameter (D50) when the cumulative value in the volume-based cumulative particle size distribution obtained by the laser diffraction scattering method for the powder reaches 50%.
• the laser analysis scattering method is measured according to the method described in ISO 13320:2009.
• a laser diffraction scattering particle size distribution analyzer or the like can be used.
• LS-13 320 product name
• Beckman Coulter, Inc. Beckman Coulter, Inc.
• the boron nitride powder preferably has a purity of 98.5% by mass or more, an average particle diameter of 10 to 90 ⁇ m, and a crushing strength of aggregated particles of 5 MPa or more, from the viewpoint of the insulating properties of the resin sealing material. .
• a resin encapsulant according to one embodiment is a resin encapsulant for a semiconductor memory and contains the boron nitride powder according to the above embodiment.
• resins used for resin sealing materials can be used.
• resins include liquid crystal polymers, fluororesins, silicone resins, silicone rubbers, acrylic resins, polyolefins (polyethylene, etc.), epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, polyimides, polyamideimides, poly Etherimide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, polyethersulfone, polycarbonate, maleimide-modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber, styrene) resins and AES (acrylonitrile ethylene propylene diene rubber-styrene) resins.
• the resin content may be, for example, 15% by volume or more, 20% by volume or more, or 30% by volume or more based on the total volume of the resin sealing material.
• the resin content may be, for example, 60% by volume or less, 50% by volume or less, or 40% by volume or less based on the total volume of the resin sealing material.
• the resin content may be, for example, 15 to 60% by volume, 20 to 50% by volume, or 30 to 40% by volume based on the total volume of the resin sealing material.
• the content of the boron nitride powder may be, for example, 30% by volume or more, 40% by volume or more, 50% by volume or more, or 60% by volume or more based on the total volume of the resin sealing material.
• the content of the boron nitride powder may be, for example, 85% by volume or less, 80% by volume or less, or 70% by volume or less based on the total volume of the resin sealing material.
• the content of the boron nitride powder is, for example, 30 to 85% by volume, 40 to 85% by volume, 40 to 80% by volume, 50 to 80% by volume, 50 to 70% by volume, based on the total volume of the resin sealing material. , or 60-70% by volume.
• the resin sealing material may further contain a curing agent for curing the resin in addition to the resin and boron nitride powder.
• the curing agent can be appropriately selected according to the type of resin.
• examples of curing agents include phenol novolac compounds, acid anhydrides, amino compounds, imidazole compounds, and the like.
• the content of the curing agent may be, for example, 0.5 parts by mass or more or 1 part by mass or more, and may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin. It may be up to 15 parts by weight or 1 to 10 parts by weight.
• Example 1 [Preparation of boron carbide powder] 100 parts by mass of orthoboric acid manufactured by Shin Nippon Denko Co., Ltd. and 35 parts by mass of acetylene black (product name: HS100L) manufactured by Denka Co., Ltd. were mixed using a Henschel mixer. The resulting mixture was filled in a graphite crucible and heated in an arc furnace at 2200° C. for 6 hours under an argon atmosphere to obtain massive boron carbide (B 4 C). The resulting mass was coarsely pulverized with a jaw crusher to obtain coarse powder. The obtained coarse powder was further pulverized by a ball mill having silicon carbide balls (diameter: 10 mm) to obtain pulverized powder.
• Pulverization by a ball mill was performed for 60 minutes at a rotation speed of 25 rpm. Thereafter, the pulverized powder was classified using a vibrating sieve with an opening of 63 ⁇ m to prepare a boron carbide powder (B 4 C powder) with an average particle size of 20 ⁇ m.
• the boron carbide powder had a specific surface area of 0.4 m 2 /g and a purity of 98% by mass.
• the average particle size of the boron carbide powder was measured according to ISO 13320:2009 using a Beckman Coulter laser diffraction scattering method particle size distribution analyzer (equipment name: LS-13 320).
• the boron carbide powder was not treated with a homogenizer.
• water was used as a solvent for dispersing the boron carbide powder, and hexametaphosphoric acid was used as a dispersant.
• a numerical value of 1.33 was used as the refractive index of water, and a numerical value of 2.6 was used as the refractive index of the boron carbide powder.
• the specific surface area of the boron carbide powder was calculated according to the description of JIS Z 8830:2013 "Method for measuring specific surface area of powder (solid) by gas adsorption", applying the BET single point method using nitrogen gas.
• a specific surface area measuring device a specific surface area measuring device manufactured by Yuasa Ionics Co., Ltd. (device name: Kantersorb) was used. The measurement was performed after the boron carbide powder was dried and degassed at 300° C. for 15 minutes.
• the purity of boron carbide powder was calculated from the sum of carbon content and boron content.
• the amount of carbon was calculated from a combustion infrared absorption method, and the amount of boron was calculated from an ICP emission analysis.
• the temperature was raised from room temperature to 1000°C at a temperature increase rate of 10°C/min, the temperature was raised from 1000°C to 1950°C at a temperature increase rate of 2°C/min, and held at 1950°C for 5 hours. Firing was performed.
• the obtained powder was pulverized 20 times with a Henschel mixer, the obtained pulverized product was classified by passing it through a sieve with an opening of 75 ⁇ m, and aggregated particles composed of aggregated primary particles of hexagonal boron nitride. to obtain the boron nitride powder of Example 1.
• the obtained boron nitride powder had a uranium content of 19 mass ppb, an orientation index of 7, a purity of 99 mass%, and an average particle size of 40 ⁇ m.
• the strength was 12 Mpa.
• the uranium content of boron nitride powder was determined by the following method.
• boron nitride powder chemical analysis method 0.5 g of a sample (boron nitride powder) was subjected to pressure acid decomposition in a mixture of nitric acid, sulfuric acid and hydrofluoric acid at 180° C. for 18 hours. Thereafter, the solution obtained by the pressure acid decomposition was dried on a hot plate to solidify, and the obtained solid content was mixed with nitric acid to obtain a mixed solution.
• ICP-MS inductively coupled plasma mass spectrometer
• the orientation index of the boron nitride powder was determined from the measurement results by the powder X-ray diffraction method.
• boron nitride powder was filled into the concave portion of a glass cell having a concave portion with a depth of 0.2 mm attached to an X-ray diffractometer (manufactured by Rigaku Co., Ltd., product name: ULTIMA-IV), and a powder sample molding machine ( Ameena Tech Co., Ltd., product name: PX700) was used to solidify at a set pressure M to prepare a measurement sample. When the surface of the filling solidified by the molding machine was not smooth, it was smoothed manually before measurement.
• the peak intensity ratio between the (002) plane and the (100) plane of boron nitride is calculated, and based on this value, the orientation index [I (002 )/I(100)] was determined.
• the purity of boron nitride powder was determined by the following method. First, boron nitride powder was alkali-decomposed with sodium hydroxide, ammonia was distilled from the decomposed solution by steam distillation, and collected in an aqueous boric acid solution. This collected liquid was subjected to titration with a normal sulfuric acid solution. The content of nitrogen atoms (N) in the boron nitride powder was calculated from the titration results. Based on the obtained nitrogen atom content, the content of boron nitride in the boron nitride powder was determined based on the formula (1), and the purity of the boron nitride powder was calculated.
• boron nitride 24.818 g/mol, and the atomic weight of nitrogen atoms is 14.006 g/mol.
• Boron nitride (BN) content [mass%] in the boron nitride powder Nitrogen atom (N) content [mass%] x 1.772 (1)
• the average particle size of the boron nitride powder was measured according to ISO 13320:2009 using a Beckman Coulter laser diffraction scattering particle size distribution analyzer (device name: LS-13 320).
• the boron nitride powder was not treated with a homogenizer.
• water was used as a solvent for dispersing the boron nitride powder, and hexametaphosphoric acid was used as a dispersant.
• a numerical value of 1.33 was used as the refractive index of water, and a numerical value of 1.80 was used as the refractive index of the boron nitride powder.
• the crushing strength of agglomerated particles was measured according to the description in JIS R 1639-5:2007 "Fine ceramics-Method for measuring (granule) properties-Part 5: Single granule crushing strength”.
• a microcompression tester manufactured by Shimadzu Corporation, product name "MCT-W500" was used.
• the measurement was performed for 20 or more aggregated particles, and the value at the time of cumulative destruction rate of 63.2% was calculated.
• Example 2 to 4 Boron nitride powders of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the firing temperature and/or firing time in the decarburization and crystallization step were changed as shown in Table 1. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 1 shows the results.
• Example 5 Pulverization with a ball mill in [Preparation of boron carbide powder] was performed for 100 minutes at a rotation speed of 100 rpm, and then classification was performed using a vibrating sieve with an opening of 34 ⁇ m, and crushing in [Decarburization and crystallization step].
• a boron nitride powder of Example 5 was obtained in the same manner as in Example 1, except that the subsequent classification was performed using a sieve with an opening of 45 ⁇ m. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 1 shows the results.
• Comparative Examples 1 and 2 Nitriding of Comparative Examples 1 and 2 was performed in the same manner as in Example 1, except that the amounts of boric acid and sodium carbonate used (based on the total mass of the raw material mixture) in the decarburization and crystallization step were changed to the values shown in Table 1. Boron powder was obtained respectively. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 1 shows the results.
• Example 6 Boron carbide powder prepared in the same manner as in Example 1 was subjected to acid treatment. Specifically, first, boron carbide powder prepared in the same manner as in Example 1 was prepared. An acid solution was then prepared by mixing a hydrofluoric acid solution and a hydrochloric acid solution. The acid concentration of the acid solution was 40% by mass, and the mass ratio of hydrofluoric acid and hydrochloric acid in the acid solution (mass ratio of HF and HCl) was 1:1 (i.e., hydrogen fluoride in the acid solution Both the acid concentration and the hydrochloric acid concentration were set to 20% by mass.).
• the acid solution was heated and maintained at 80° C., and boron carbide powder was added thereto and stirred at 80° C. for 5 hours.
• the boron carbide powder and the acid solution were brought into contact with each other, and the boron carbide powder was acid-treated.
• decantation was performed, and the operation of adding a new acid solution and performing acid treatment was repeated 15 times.
• the slurry was then dried to obtain an acid-treated boron carbide powder.
• the average particle size and purity of the obtained boron carbide powder were measured by the method described in Example 1, the average particle size was 20 ⁇ m and the purity was 99% by mass.
• Example 2 shows the results.
• Example 7 A boron nitride powder of Example 7 was obtained in the same manner as in Example 6, except that the firing temperature and firing time in the decarburization and crystallization step were changed as shown in Table 2. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 2 shows the results.
• Example 8 Same as Example 7 except that the concentration of the acid solution, the treatment temperature (the temperature of the mixture of the boron carbide powder and the acid solution), and the treatment time (stirring time) in the acid treatment step were changed to the values shown in Table 2. Then, the boron nitride powder of Example 8 was obtained. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 2 shows the results. When analyzed in the same manner as uranium, the amount of thorium was 4 mass ppb.
• Example 9 Except for changing the concentration of the acid solution, the composition of the acid solution, the treatment temperature (the temperature of the mixture of the boron carbide powder and the acid solution), and the treatment time (stirring time) in the acid treatment step to the values shown in Table 2, Boron nitride powder of Example 9 was obtained in the same manner as in Example 6. Further, in the same manner as in Example 1, the uranium content, orientation index, purity and average particle size of the boron nitride powder, and the crushing strength of aggregated particles in the boron nitride powder were measured. Table 2 shows the results.

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