WO2021235530A1

WO2021235530A1 - Spherical crystalline silica particles and method for producing same

Info

Publication number: WO2021235530A1
Application number: PCT/JP2021/019250
Authority: WO
Inventors: 睦人田中; 竜太郎沼尾; 泰宏青山; 一彦楠; 昌史牛尾
Original assignee: 日鉄ケミカル＆マテリアル株式会社
Priority date: 2020-05-20
Filing date: 2021-05-20
Publication date: 2021-11-25
Also published as: KR20230011937A; CN115697907A; JPWO2021235530A1; TW202200499A

Abstract

(Problem) To provide: spherical silica particles which are suitable for use as a filler for a semiconductor sealing material having excellent dielectric properties in the millimeter wave band, i.e., spherical crystalline silica particles which are reduced in the contents of an alkali metal and an alkaline earth metal to lower levels and have a high crystallization rate and a high quartz content; and a method for producing the spherical crystalline silica particles. (Solution) Provided are spherical crystalline silica particles each having a degree of circularity of 0.80 or more, containing lithium in an amount of 0.02% by mass or more and less than 0.40% by mass in terms of oxide content, also containing calcium in an amount of 0.004% by mass or more and less than 1.0% by mass in terms of oxide content, and also containing a crystalline silica phase, in which the content ratio of the crystalline silica phase in the spherical crystalline silica particles is 40.0% or more, and the content ratio of quarts in the crystalline silica phase is 80.0% by mass or more.

Description

Spherical crystalline silica particles and their manufacturing method

The present invention relates to spherical crystalline silica particles and a method for producing the same, particularly spherical crystalline silica particles having a high proportion of quartz and a method for producing the same.

The frequency is increasing due to the increase in the amount of information due to the sophistication of communication technology and the rapid expansion of the use of millimeter wave bands such as millimeter wave radar. The circuit board that transmits these high-frequency signals is composed of an electrode and a dielectric board that form a circuit pattern. In order to suppress energy loss during transmission of high-frequency signals, it is necessary that the dielectric loss tangent (tan δ) of the dielectric material is small. For low dielectric loss, the dielectric material must have low polarity and a low dipole moment.

As the dielectric material, ceramic particles, resins, and composites obtained by combining them are mainly used. In particular, with the recent expansion of the use of the millimeter wave band, ceramic particles and resins having a lower dielectric loss tangent (tan δ) are required. The resin has a relatively small relative permittivity (εr) and is suitable for high-frequency devices, but has a dielectric loss tangent (tan δ) and a coefficient of thermal expansion larger than those of ceramic particles. For this reason, the composite of the ceramic particles for the millimeter wave band and the resin is (1) made into a low dielectric loss tangent (tan δ) of the ceramic particles themselves, and (2) is highly filled with the ceramic particles and has a large dielectric loss tangent (tan δ). It is suitable to reduce the amount of resin shown.

Silica (SiO ₂ ) particles have been conventionally used as ceramic particles. If the shape of the silica particles is angular, the fluidity, dispersibility, and filling property in the resin are deteriorated, and the manufacturing equipment is also worn. In order to improve these, spherical silica particles are widely used. It is considered that the closer the spherical silica particles are to a true sphere, the better the filling property, fluidity, and mold wear resistance in the resin, and particles having high roundness have been pursued. Furthermore, further improvement of filling property has been studied by optimizing the particle size distribution of the particles.

Generally, the thermal spraying method is used as a method for producing spherical silica. In thermal spraying, the particles are melted by passing them through a high temperature region such as a flame, and the shape of the particles becomes spherical due to surface tension. The melted spheroidized particles are collected by airflow so that the particles do not fuse with each other, but the particles after thermal spraying are rapidly cooled. Since silica is rapidly cooled from the molten state, silica does not crystallize, has an amorphous structure, and becomes glass-like particles generally called quartz glass.

Since the spherical silica particles produced by the thermal spraying method are amorphous, their thermal expansion rate and thermal conductivity are low. The coefficient of thermal expansion of the amorphous silica particles is 0.5 ppm / K, and the thermal conductivity is 1.4 W / mK. These physical properties are substantially the same as the coefficient of thermal expansion of quartz glass having an amorphous structure without having a crystal structure. Generally, the coefficient of thermal expansion of Si, which is the main raw material of the IC chip, is 3 to 5 ppm / K, and the coefficient of thermal expansion of the sealing resin for encapsulating the IC chip is extremely larger than that of Si. Due to the difference in thermal expansion behavior between Si and the sealing resin, the IC chip warps, which hinders production. On the other hand, when a resin having a large coefficient of thermal expansion is highly filled with spherical silica having a small coefficient of thermal expansion, the effect of reducing the thermal expansion of the sealing material (composite of spherical silica and resin) itself can be obtained. By setting the coefficient of thermal expansion of the encapsulant to a value close to Si, it is possible to suppress deformation due to the thermal expansion behavior when encapsulating the IC chip.

As described above, the characteristics required for silica particles for encapsulants include filling property, fluidity, and mold abrasion resistance, which can be blended in a large amount with a resin to maintain the performance as a composite. , Excellent dielectric properties of high frequencies in the millimeter wave band. Since the dielectric property is a physical property value of the material, it is difficult to reduce the dielectric loss tangent of the amorphous silica particles.

Patent Document 1 is characterized in that a Zn compound is added in an amount of 0.5% by mass or more in terms of ZnO to silica gel having an average particle size of 0.1 to 20 μm, and this mixture is heat-treated at 900 to 1100 ° C. A method for producing a porous powder having a main crystal phase of quartz is described.

Patent Document 2 describes an oxide of an alkali metal compound in amorphous spherical silica particles with respect to the total mass of the mass of the amorphous spherical silica particles and the mass of the alkali metal converted into oxides. Mix at a ratio of 0.4 to 5% by mass in terms of, or with respect to the total mass of the alkaline earth metal in terms of the mass of the amorphous spherical silica particles and the alkali earth metal in terms of oxide. Spherical silica particles mixed in an oxide equivalent of 1 to 5% by mass are heat-treated at 800 ° C. to 1300 ° C. to cool the heat-treated spherical silica particles, and the cooled spherical silica particles are 90% by mass or more. A method for producing spherical crystalline silica particles, which has the crystal phase of the above and is characterized in that the amount of quartz crystals is 70% by mass or more of the whole, is shown. However, if the amount of alkali metal added is less than 0.4% by mass and the amount of alkaline earth metal is less than 1% by mass, the appearance probability of quartz is low.

In Non-Patent Document 1, alkali metal oxides are systematically added to the synthesized amorphous spherical silica to form pellets, and then heat treatment is performed to examine the effects of crystallization and phase transition due to the additives. .. According to this, when the additive is lithium oxide (Li ₂ O), it is shown that quartz can be obtained by adding 0.5% by mass or more and firing at 800 ° C. or higher.

Non-Patent Document 2 investigates the effect of cations on the crystallization and phase transition of silica substances. Among them, it has been shown that quartz appears as the most dominant phase by adding 10% LiCl by mass to the synthesized amorphous silica and heat-treating it at 800 ° C.

Japanese Unexamined Patent Publication No. 2002-20111 International Publication No. 2018/186308

The present inventors have aimed to search for filler particles for semiconductor encapsulation having excellent dielectric properties in the millimeter-wave band having a frequency of 30 GHz to 80 GHz, and to fabricate a resin composite for high-frequency devices by mixing them with a resin. .. As a result, it was found that it is effective to first heat-treat and crystallize spherical molten (amorphous) silica in order to obtain a resin composite having a low dielectric loss tangent. That is, it was confirmed that the dielectric loss tangent in the millimeter wave band (30 GHz to 80 GHz) of crystalline silica is significantly lower than that of amorphous silica which has been widely used in the past. As a result, the spherical crystalline silica particles become silica particles exhibiting excellent dielectric properties for high-frequency device applications. The crystalline silica obtained by heat treatment is quartz, cristobalite or a mixture thereof. Since quartz and cristobalite have different physical characteristics, the crystalline silica phase is preferably a single phase when used as a filler.

Further, when crystallized into cristobalite, the coefficient of thermal expansion of cristobalite becomes more than three times that before the heat treatment, and further, since it has a pole near 250 ° C., various problems in use occur. In particular, when used as a filler for semiconductor encapsulation, peeling occurs at the interface between the element and the encapsulant due to a mismatch in thermal expansion behavior with the semiconductor element. Among crystalline silicas, quartz whose thermal expansion pole is outside the mounting temperature range is suitable for such applications. When quartz is used as a filler for semiconductor encapsulation, it is possible to improve the mounting reliability while achieving a low dielectric loss and an appropriate coefficient of thermal expansion.

As a method for obtaining quartz by crystallizing spherical amorphous silica, in Patent Document 1, 0.5% by mass or more of a zinc compound is added in terms of oxide, and this mixture is heat-treated at 900 to 1100 ° C. Is disclosed. However, as a result of the reproduction test by the present inventors, crystallization itself did not proceed at the heat treatment temperature of 950 ° C. or lower, and it remained amorphous silica. When the heat treatment was performed above 950 ° C, crystallization started to proceed, but the crystallinity remained at about 20% even at 1100 ° C. In addition, the crystal phase that appeared was mainly cristobalite, and a single phase of quartz could not be obtained with a high content.

In Patent Document 2, spherical silica particles mixed in an oxide equivalent of 1 to 5% by mass with respect to the total mass of the alkali earth metal in terms of oxide are heat-treated at 800 ° C to 1300 ° C. Spherical crystals comprising a step of cooling the cooled spherical silica particles, wherein the cooled spherical silica particles have a crystal phase of 90% by mass or more, and the quartz crystals are 70% by mass or more of the whole. A method for producing quality silica particles is shown. Calcium is shown as an alkaline earth metal in the examples, but when 0.5% by mass of calcium, which is a comparative example, is added and heat-treated at 1100 ° C., the appearance of quartz is less than 30%. Low. Further, when calcium is added in an amount of less than 1% by mass in terms of oxide, spherical crystalline silica having a high quartz content has not been obtained so far.

Further, in Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2, lithium is similarly shown as a quartz crystallization promoting element. Patent Document 2 discloses that the mixture is mixed at a ratio of 0.4 to 5% by mass in terms of lithium oxide and heat-treated at 800 ° C to 1300 ° C. Non-Patent Document 1 shows that quartz can be obtained by adding 0.5% by mass or more of lithium oxide to the synthesized amorphous spherical silica and firing it at 800 ° C. or higher. Further, Non-Patent Document 2 shows that 10% by mass of lithium chloride (LiCl) is added to the synthesized amorphous silica and heat-treated at 800 ° C. to allow quartz to appear as the most dominant phase.

However, alkaline earth metals such as calcium and alkali metals such as lithium are not preferable as additives to the semiconductor encapsulant. From the viewpoint of normal operation of semiconductor devices and maintenance of mounting reliability, it is necessary to reduce the amount of alkaline earth metal and alkali metal element added.

Temperature, pressure, and impurity elements are well known as factors that affect the crystallization of amorphous silica. Regarding the influence of pressure, for example, Non-Patent Document 3 describes that when heat treatment is performed at 300 ° C to 1200 ° C under 20,000 to 30,000 atm, it crystallizes into quartz, but a pressurizing device at tens of thousands of atmospheres. Is not preferable because the amount of processing is limited and it is difficult to carry out mass production industrially. Although there have been many reports of crystallization experiments using temperature and impurity elements as variable factors, spherical crystals having a crystalline silica content of 40% or more and a quartz ratio of 80% by mass or more in the crystalline silica have been reported so far. No quality silica has been obtained. From the viewpoint of normal operation of semiconductor devices and maintenance of mounting reliability, lithium and silica are reduced to less than 0.40% by mass and less than 1.0% by mass in terms of oxides, respectively, while having a high crystallization rate and substantially. It has been required to obtain silica particles composed of a single quartz phase.

INDUSTRIAL APPLICABILITY The present invention has a high crystallization rate while keeping the content of spherical silica particles, that is, alkali metal and alkaline earth metal, suitable as fillers for semiconductor encapsulants having excellent dielectric properties in the millimeter wave band low. It is an object of the present invention to provide spherical crystalline silica particles having a high proportion of quartz and a method for producing the same.

The inventor of the present application has studied diligently for the purpose of solving the above problems. As a result, the powder composed of amorphous silica particles having a circularity of 0.80 or more contains a calcium raw material containing 0.004 or more and less than 1.0% by mass of calcium in terms of oxide, and lithium as an oxide. By heating a mixed raw material powder obtained by mixing both a lithium raw material containing 0.02% by mass or more and less than 0.40% by mass in terms of heat at a heat treatment temperature of 850 ° C to 1150 ° C, each of lithium and calcium can be obtained. We succeeded in promoting quartz crystallization while reducing the content compared to the conventional method. Although not bound by a specific theory, the simultaneous addition of lithium metal and calcium metal to silica exerts a synergistic effect on quartz crystallization, and is added compared to the case where each element is added alone. It is considered that the crystallization of quartz was promoted despite the reduction of the amount. The crystalline silica particles obtained by the heat treatment at 850 to 1150 ° C. contain a crystalline silica phase, and the crystalline silica phase is substantially a quartz single phase. The term "single phase" as used herein means that the proportion of quartz in the crystalline silica phase is 80% by mass or more, preferably 85.0% by mass or more, and more preferably 90.0% by mass or more.

The present invention provides the following spherical silica particles and a method for producing the same.
(1) The circularity is 0.80 or more, lithium is contained in an oxide equivalent of 0.02% by mass or more and less than 0.40% by mass, and calcium is contained in an oxide equivalent of 0.004% by mass or more and 1.0% by mass. % Of the spherical crystalline silica particles containing the crystalline silica phase, the ratio of the crystalline silica phase to the spherical crystalline silica particles is 40.0% or more, and the above-mentioned Spherical crystalline silica particles in which the proportion of quartz in the crystalline silica phase is 80.0% by mass or more.
(2) The spherical crystalline material according to (1), wherein the ratio of the crystalline silica phase is 70.0% or more, and the ratio of quartz to the crystalline silica phase is 85.0% by mass or more. Silica particles.
(3) The spherical crystalline material according to (2) above, wherein the ratio of the crystalline silica phase is 80.0% or more, and the ratio of quartz to the crystalline silica phase is 90.0% by mass or more. Silica particles.
(4) The spherical crystalline silica particle according to any one of (1) to (3) above, wherein the average particle size (D50) is 3 to 100 μm.
(5) The method for producing spherical crystalline silica particles according to any one of (1) to (4), which comprises a spherical amorphous silica particles having a circularity of 0.80 or more, a calcium raw material, and a calcium raw material. A method for producing spherical crystalline silica particles, which comprises heat-treating a mixed raw material powder obtained by mixing a lithium raw material at 850 ° C to 1150 ° C.
(6) The method for producing spherical crystalline silica particles according to any one of (1) to (4).
It comprises heat-treating a mixed raw material powder obtained by mixing a lithium raw material with spherical amorphous silica particles having a circularity of 0.80 or more and containing a calcium component at 850 ° C to 1150 ° C. A method for producing spherical crystalline silica particles.
(7) The method for producing spherical crystalline silica particles according to any one of (1) to (4).
The present invention comprises heat-treating a mixed raw material powder obtained by mixing a calcium raw material with spherical amorphous silica particles having a circularity of 0.80 or more and containing a lithium component at 850 ° C to 1150 ° C. A method for producing spherical crystalline silica particles.
(8) The method for producing spherical crystalline silica particles according to any one of (1) to (4).
A method for producing spherical crystalline silica particles, which comprises heat-treating spherical amorphous silica particles having a circularity of 0.80 or more and containing a calcium component and a lithium component at 850 ° C to 1150 ° C.
(9) The method for producing spherical crystalline silica particles according to any one of (5) to (8), wherein the heat treatment temperature is 875 ° C to 1110 ° C.

According to the present invention, spherical silica particles suitable for use as a filler for semiconductor encapsulants having excellent dielectric properties in the millimeter wave band, that is, high crystals while keeping the content of alkali metal and alkaline earth metal low. It is possible to provide spherical crystalline silica particles having a high crystallization rate and a high proportion of quartz, and a method for producing the same.

FIG. 1 is an XRD pattern of amorphous silica before heat treatment and silica (after heat treatment) according to one aspect of the present invention.

The spherical crystalline silica according to one aspect of the present invention has a circularity of 0.80 or more, contains lithium in an oxide equivalent of 0.02% by mass or more and less than 0.40% by mass, and contains calcium in an oxide equivalent of 0. Spherical crystalline silica particles containing .004% by mass or more and less than 1.0% by mass and containing a crystalline silica phase, wherein the ratio of the crystalline silica phase to the spherical crystalline silica particles is 40. Spherical crystalline silica particles having a content of 0.0% or more and a ratio of quartz in the crystalline silica phase of 80.0% by mass or more. The phase of crystalline silica referred to here is 40.0% or more is the ratio of the phase of crystalline silica to the spherical crystalline silica particles, and the method for obtaining the phase will be described later.

The crystal structure of silica (SiO ₂ ) includes cristobalite, quartz and the like. Silica having these crystal structures has a higher thermal conductivity than amorphous silica. Therefore, in the filler for semiconductor encapsulation, the heat dissipation from the IC chip can be improved by replacing amorphous silica with crystalline silica in an appropriate amount. Further, since crystalline silica has a low dielectric loss tangent in the millimeter wave band, the dielectric loss tangent of the semiconductor encapsulant decreases as more amorphous silica is replaced with crystalline silica in the semiconductor encapsulating filler.

[Manufacturing method of spherical crystalline silica particles]
The spherical crystalline silica particles of the present invention may be produced by mixing spherical amorphous silica with both a calcium raw material and a lithium raw material and heat-treating the mixture (also referred to as a mixed raw material).
According to one aspect, a mixed raw material obtained by mixing a lithium raw material with spherical amorphous silica particles containing a calcium component may be heat-treated.
Alternatively, the mixed raw material obtained by mixing the calcium raw material with the spherical amorphous silica particles containing a lithium component may be heat-treated.
Alternatively, it may be produced by heat-treating spherical amorphous silica particles containing a calcium component and a lithium component.

(Spherical amorphous silica particles)
Amorphous spherical silica particles as a raw material can be produced by a method such as a thermal spraying method. In the thermal spraying method, natural silica powder pulverized and adjusted to a desired particle size is passed through a flame to melt the particles, and the shape of the particles becomes spherical due to surface tension. By such a thermal spraying method, spherical amorphous silica particles having a circularity of 0.80 or more can be produced.
The composition of the spherical amorphous silica particles is not particularly limited as long as the main component is silica and the finally obtained spherical crystalline silica particles are in a desired range. As one aspect, the composition of the spherical amorphous silica particles may be 98.0% by mass or more of silica (SiO ₂ ), and Ca, Li, Al, Na, Mg, Ba as trace-containing elements. , Zn and the like may be included. In one aspect, the composition of the spherical amorphous silica particles may contain less than 0.5% by weight of Zn.

(Calcium raw material)
The calcium raw material is mixed with spherical amorphous silica particles and heat-treated. The composition and mixing amount of the calcium raw material are not particularly limited as long as the finally obtained spherical crystalline silica particles are in a desired range, and are appropriately adjusted. The calcium raw material may be calcium hydroxide, calcium oxide or the like that are stably present in the atmosphere, or may be natural minerals. The calcium raw material can be added in the form of powder, aqueous solution or the like so as to be uniformly mixed with the spherical amorphous silica particles. Further, at least a part of the calcium raw material may be a trace element contained in the spherical amorphous silica particles. For example, if the spherical amorphous silica particles sufficiently contain calcium and the finally obtained spherical crystalline silica particles have a desired calcium content, the spherical amorphous silica particles can be used as a calcium raw material. May be combined with. Further, when the spherical amorphous silica particles contain calcium but are not sufficient, a calcium raw material can be added so that the finally obtained spherical crystalline silica particles have a desired calcium content.

(Lithium raw material)
The lithium raw material is mixed with spherical amorphous silica particles and heat-treated. The composition and mixing amount of the lithium raw material are not particularly limited as long as the finally obtained spherical crystalline silica particles are in a desired range, and are appropriately adjusted. The form of adding the lithium raw material, such as an oxide, a carbonic acid oxide, a hydroxide, and a nitric acid oxide, is not particularly limited. It can be added in the form of a powder, an aqueous solution, or the like so as to be uniformly mixed with the amorphous spherical silica particles. Further, at least a part of the lithium raw material may be a trace element contained in the spherical amorphous silica particles. For example, if the spherical amorphous silica particles sufficiently contain lithium and the finally obtained spherical crystalline silica particles have a desired lithium content, the spherical amorphous silica particles can be used as a lithium raw material. May be combined with. Further, when the spherical amorphous silica particles contain lithium but are not sufficient, a calcium raw material can be added so that the finally obtained spherical crystalline silica particles have a desired lithium content.

(mixture)
The spherical amorphous silica particles are mixed with both a calcium raw material and a lithium raw material. The calcium raw material and / or the lithium raw material may be contained in spherical amorphous silica. The mixing method is not particularly limited as long as each raw material is evenly dispersed and mixed in the mixture. Mixing may be performed by a powder mixer. By mixing, the calcium raw material and the lithium raw material come into contact with at least a part of the spherical amorphous silica, and in the subsequent heat treatment step, the crystallization of the spherical amorphous silica, particularly the crystallization into quartz, is promoted.
At the time of mixing, the lithium contained in the produced spherical crystalline silica particles is 0.02% by mass or more and less than 0.40% by mass in terms of oxide, and the calcium contained is in terms of oxide. Each raw material is mixed and mixed so as to be 0.004% by mass or more and less than 1.0% by mass. Since the total amount of the blended lithium raw material and calcium raw material is not contained in the produced spherical crystalline silica particles, it is preferable to blend them in consideration of the content ratio.
In addition, since the mixing is such that the calcium raw material and the lithium raw material are brought into contact with at least a part of the spherical amorphous silica and does not promote the pulverization of the spherical amorphous silica, the circularity thereof is the mixing. There is almost no decrease before and after.

(Heat treatment)
The temperature for heat-treating the mixed raw material obtained by mixing the spherical amorphous silica particles, the calcium raw material and the lithium raw material is in the temperature range of 850 ° C to 1150 ° C. The atmosphere during the heat treatment can be an oxidizing atmosphere such as the atmosphere and an inert gas atmosphere such as nitrogen or argon. Atmospheric pressure is preferably atmospheric pressure because it is industrially heat-treated in large quantities. If the heat treatment temperature is lower than 850 ° C., crystallization does not proceed or is extremely slow. On the other hand, when the temperature is higher than 1150 ° C., the crystallization of cristobalite proceeds competitively with the quartz crystallization. As a result, it becomes impossible to obtain spherical crystalline silica particles which are substantially single-phase quartz. Here, the substantially single phase refers to a state in which the quartz phase occupies 80% by mass or more in the crystalline silica phase contained in the spherical crystalline silica particles. Preferably, the heat treatment temperature is 875 ° C to 1110 ° C.

The time of the heat treatment can be appropriately adjusted so that the desired degree of crystallinity can be obtained. When the lithium element and the calcium element are uniformly present together in the spherical amorphous silica particles, the quartz crystallization of the spherical amorphous silica particles proceeds due to the synergistic effect of the two elements as compared with the case where a single element is present. In one aspect of the present invention, lithium may be added as a lithium raw material (lithium carbonate or the like) at the time of mixing, or may be contained in the spherical amorphous silica particles in advance. Further, calcium may be supplied as a calcium raw material (calcium oxide or the like) at the time of mixing, or may be contained in the spherical amorphous silica particles in advance. Since the lithium and calcium are uniformly present in the spherical amorphous silica particles due to diffusion by the heating step, it is considered that the entire spherical amorphous silica particles crystallize into quartz. Therefore, as the heat treatment time becomes longer, lithium and calcium diffuse into the spherical amorphous silica particles, so that crystallization proceeds. Typically, in other words, when the ascending / descending temperature is greater than 60 ° C./hour, the crystallization progress is substantially determined by the heat treatment temperature, i.e., the retention time at maximum temperature, so crystallization control is at maximum temperature. The holding time may be adjusted. In that case, the heat treatment time may be adjusted in the range of approximately 1 hour to 48 hours, and may be 3 hours or more or 6 hours or more from the viewpoint of sufficiently promoting crystallization. Further, since the crystallinity is saturated even if the heat treatment time is excessively extended, the heat treatment time may be 25 hours or less, 18 hours or less, or 12 hours or less from the viewpoint of cost reduction.
Further, as the heat treatment temperature increases, the mass diffusivity of the lithium element in the spherical amorphous silica particles increases, so that quartz crystallization proceeds. However, when the temperature exceeds 1150 ° C., the cristobalite phase appears competitively and quartz is no longer a single phase, so that there is an upper limit to the heat treatment temperature.
Further, since the degree of diffusion varies depending on the type and amount of the lithium raw material and the calcium raw material added, a suitable heat treatment time and temperature may be appropriately selected according to them.
The rate of temperature rise and the rate of cooling do not significantly affect the appearance of spherical crystalline silica particles when the heat treatment is performed in an electric furnace.

The circularity of the spherical crystalline silica of the present invention hardly decreases before and after the heat treatment for crystallization. The spherical crystalline silica particles of the present invention are crystallized at a relatively low temperature by heat treatment at 850 ° C to 1150 ° C, and the circularity hardly decreases in this temperature range. Amorphous silica particles may be bonded by fusion or sintering when the temperature exceeds 1100 ° C., but the spherical crystalline silica particles of the present invention are crystallized at 850 ° C to 1150 ° C (already). Since it is not amorphous), it is possible to completely suppress the bonding of particles due to fusion or sintering.

[Spherical crystalline silica particles]
(Circularity)
The spherical crystalline silica particles of the present invention have a circularity of 0.80 or more.
When the circularity is less than 0.80, the fluidity, dispersibility, and filling property are not sufficient when used as silica particles or the like of a resin composite composition for a semiconductor encapsulant, and the encapsulant is produced. Equipment wear may be accelerated. The average circularity of the spherical amorphous silica particles obtained by thermal spraying may be 0.80 or more. Since the temperature in the heat treatment step for crystallization is 850 to 1150 ° C., the circularity of the silica particles hardly changes before and after the heat treatment. If it is a thermal spraying method, particles having a high average circularity can be easily obtained. As a result, the method of the present invention can realize desired spherical crystalline silica particles having a high degree of circularity. From the viewpoint of improving fluidity, dispersibility, filling property, and reducing wear of equipment, the higher the circularity is, the more preferable it is, and it may be 0.85 or more, or 0.90 or more. On the other hand, since it may be difficult to make the circularity 1.0, that is, a perfect circle, the upper limit of the circularity may be 0.99 or less or 0.97 or less.

The circularity is obtained by "perimeter of the circle corresponding to the projected area of the photographed particle ÷ perimeter of the image of the photographed particle", and it means that the closer this value is to 1, the closer to the true sphere. The circularity of the present invention was determined by a flow-type particle image analysis method. In the flow-type particle image analysis method, spherical crystalline silica particles are flowed into a liquid and imaged as a still image of the particles, and image analysis is performed based on the obtained particle image to obtain the circularity of the spherical crystalline silica particles. The average value of these plurality of circularities was defined as the average circularity. If the number of particles when measuring the average circularity by the flow type particle image analysis method is too small, the average value cannot be obtained correctly. At least 100 or more particles are required, preferably 500 or more, and more preferably 1000 or more. In the present invention, about 100 particles were used by using the flow type particle image analyzer "FPIA-3000" (manufactured by Spectris). The circularity of the spherical amorphous silica particles is also determined in the same manner.

(composition)
In the spherical crystalline silica particles of the present invention, based on the mass of the silica particles (100% by mass), lithium is 0.02% by mass or more and less than 0.40% by mass in terms of oxide, and calcium is converted into oxide. It contains 0.004% by mass or more and less than 1.0% by mass. The lower limit of lithium is preferably 0.05% by mass, more preferably 0.10% by mass, and even more preferably 0.25% by mass. Further, the upper limit of lithium is preferably less than 0.35% by mass, and more preferably less than 0.30% by mass. The preferable lower limit of calcium is 0.20% by mass, and more preferably 0.6% by mass. Further, the upper limit of calcium is preferably 0.9% by mass, and more preferably 0.8% by mass. The content of lithium and calcium can be measured, for example, by atomic absorption spectrometry, ICP mass spectrometry (ICP-MS). Specifically, it was measured using ICP-MS (“7700X” manufactured by Agilent) in accordance with JIS-K0133. An aqueous solution in which silica particles were completely dissolved with hydrofluoric acid was used as a sample. Here, the content of the impurity element contained in the silica particles was defined as the content of the impurity element in the silica solution. As the calibration curve, a base solution containing only reagents may be used. By performing a specific heat treatment with a composition containing lithium and calcium in the above range, spherical crystalline silica particles composed of a single phase having a high crystallization rate and a substantially high proportion of quartz can be obtained. be able to. Lithium and calcium become almost in the form of oxides through heat treatment in the temperature range of 850 to 1150 ° C. for crystallization, after which they react with silica to incorporate lithium and calcium into the silica structure. The content thereof does not change much before and after the heat treatment in the above temperature range. When the lithium and calcium contents change before and after the heat treatment, the composition of the raw materials is adjusted so that the finally obtained spherical crystalline silica particles have the predetermined lithium and calcium contents in consideration of the degree of the change. It can be adjusted as appropriate.

(Crystal properties)
The spherical crystalline silica particles of the present invention contain a phase of crystalline silica, and the ratio of the phase of the crystalline phase silica to the spherical crystalline silica particles is 40.0% or more, and the crystalline silica is present. The proportion of quartz in the phase is 80.0% by mass or more.
When the silica particles obtained by the heat treatment are composed of amorphous and crystalline silica, it refers to the abundance ratio of amorphous and crystalline silica (so-called "crystallinity", and is referred to as such in the present specification. The type of crystalline silica and its ratio can be determined by XRD. In the XRD measurement, the ratio of the crystalline phase can be obtained by calculating from the sum of the integrated intensities of the crystalline peaks (Ic) and the integrated intensities of the amorphous halo portion (Ia) by the following formula. More specifically, the ratio of the phase of crystalline silica contained in the spherical crystalline silica particles can be obtained.
X (crystal phase ratio) = Ic / (Ic + Ia) × 100 (%)
In the present invention, XRD measurement was carried out in the range of 2Θ = 10 ° to 90 °. The crystal phase ratio was obtained from the sum of the crystalline peak intensities appearing in the 2Θ measurement range and the integrated intensity of the halo portion due to the broad amorphous appearing near 2Θ = 22 °.
Further, the types of crystal phases such as cristobalite and quartz and their respective ratios (mass%) can be obtained by quantitative analysis by X-ray diffraction. In the present invention, the quantitative analysis by X-ray diffraction was performed by using the analysis method by the Rietveld method, and the quantitative analysis was performed without using a standard sample. In the present invention, an X-ray diffractometer "D2 PHASER" (manufactured by Bruker) was used. Quantitative analysis of the crystal phase by the Rietveld method was performed by the crystal structure analysis software "TOPAS" (manufactured by Bruker).

The spherical crystalline silica particles of the present invention contain a phase of crystalline silica, and the ratio of the phase of the crystalline silica to the spherical crystalline silica particles is 40.0% or more, that is, 40.0%. It has the above-mentioned high crystallinity, and its dielectric positive contact is significantly lower than that of amorphous silica, which is preferable. From the viewpoint of reducing the dielectric loss tangent, the higher the crystallinity is, the more preferable it is, and it may be 70.0% or more, and more preferably 80.0% or more.

The spherical crystalline silica particles of the present invention contain a phase of crystalline silica, and the proportion of quartz in the phase of the crystalline silica is high, 80.0% by mass or more, and is substantially a single quartz phase. Therefore, various characteristics such as the coefficient of thermal expansion and the thermal conductivity of the spherical crystalline silica particles are substantially determined by the characteristics of quartz, that is, they do not fluctuate, and are preferable when used as a filler or the like. From the above viewpoint, the higher the proportion of quartz, the more preferable it is, and it may be 85.0% by mass or more, and more preferably 90.0% by mass or more.

(Average particle size)
In one aspect of the present invention, the average particle size (D50) of the spherical crystalline silica particles may be 3 to 100 μm. If the average particle size is less than 3 μm, the cohesiveness of the particles becomes large and the fluidity is remarkably lowered, which is not preferable. If the average particle size exceeds 100 μm, voids between the particles tend to remain and it becomes difficult to improve the filling property, which is not preferable. More preferably, the average particle size is in the range of 10 to 80 μm. The particle size of the spherical amorphous silica particles before the heat treatment hardly changes before and after the heat treatment in the temperature range of 850 to 1150 ° C.

For the average particle size (D50), a median diameter D50 having a cumulative volume of 50% was determined in a volume-based particle size distribution measured by a laser diffraction / scattering type particle size distribution measurement method. The laser diffraction / scattering type particle size distribution measurement method is a method in which a dispersion liquid in which spherical crystalline silica particles are dispersed is irradiated with laser light, and the particle size distribution is obtained from the intensity distribution pattern of the diffraction / scattering light emitted from the dispersion liquid. Is. In the present invention, a laser diffraction / scattering type particle size distribution measuring device "CILAS920" (manufactured by Cirrus) was used. The average particle size of the spherical amorphous silica particles can be obtained in the same manner.

(Application example)
INDUSTRIAL APPLICABILITY According to the present invention, it is possible to produce a composite composition of finally obtained spherical crystalline silica particles and a resin, and further a resin composite obtained by curing the resin composite composition. The composition of the resin composite composition will be described below.

A resin composite composition such as a semiconductor encapsulant (particularly a solid encapsulant) and an interlayer insulating film can be obtained by using a slurry composition containing spherical crystalline silica particles and a resin. Further, by curing these resin complex compositions, a resin complex such as a sealing material (cured body) and a substrate for a semiconductor package can be obtained.

In the case of producing the resin composite composition, for example, in addition to the spherical crystalline silica particles and the resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent and the like are blended as necessary, and known for kneading and the like. Complex by method. Then, it is molded according to the application such as pellet form or film form.

Further, when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition is melted by applying heat to be processed into a shape suitable for the intended use, and the heat is higher than that at the time of melting. In addition, it is completely cured. In this case, a known method such as a transfer molding method can be used. It was

For example, when manufacturing a semiconductor-related material such as a packaging substrate or an interlayer insulating film, a known resin can be applied as the resin used for the resin composite composition, but it is preferable to use an epoxy resin. The epoxy resin is not particularly limited, but for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene type epoxy resin, phenoxy type epoxy resin and the like. Can be used. One of these can be used alone, or two or more having different molecular weights can be used in combination. Among these, an epoxy resin having two or more epoxy groups in one molecule is preferable from the viewpoint of curability, heat resistance and the like. Specifically, biphenyl type epoxy resin, phenol novolac type epoxy resin, orthocresol novolak type epoxy resin, epoxidized phenols and aldehydes novolak resin, glycidyl ether such as bisphenol A, bisphenol F and bisphenol S, Glycidyl ester acid epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, alkyl-modified polyfunctionality obtained by the reaction of polybasic acids such as phthalic acid and dimer acid with epochlorhydrin. Epoxy resin, β-naphthol novolac type epoxy resin, 1,6-dihydroxynaphthalene type epoxy resin, 2,7-dihydroxynaphthalene type epoxy resin, bishydroxybiphenyl type epoxy resin, bromine to impart flame retardancy, etc. Examples thereof include an epoxy resin into which the halogen of the above is introduced. Among the epoxy resins having two or more epoxy groups in one of these molecules, the bisphenol A type epoxy resin is particularly preferable.

Further, as a resin used for a resin composite composition such as a prepreg for a printed circuit board and various engineer plastics for applications other than the composite material for a semiconductor encapsulant, a resin other than an epoxy-based resin can also be applied. Specifically, in addition to epoxy resin, polyamide such as silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, etc.; polybutylene terephthalate, polyethylene terephthalate, etc. Polyester; Polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber / styrene) resin, AES (acrylonitrile / ethylene / propylene / diene rubber-styrene) ) Resin is mentioned.
As the curing agent used in the resin composite composition, a known curing agent may be used for curing the resin, but for example, a phenol-based curing agent can be used. As the phenol-based curing agent, a phenol novolac resin, an alkylphenol novolak resin, polyvinylphenols and the like can be used alone or in combination of two or more.

The compounding amount of the phenol curing agent is preferably 0.1 or more and less than 1.0 in the equivalent ratio (phenolic hydroxyl group equivalent / epoxy group equivalent) with the epoxy resin. As a result, the unreacted phenol curing agent does not remain, and the hygroscopic heat resistance is improved.

The amount of the spherical crystalline silica particles of the present invention added to the resin composite composition is preferably large from the viewpoint of heat resistance and coefficient of thermal expansion, but is usually 70% by mass or more and 95% by mass or less, preferably 80% by mass. % Or more and 95% by mass or less, more preferably 85% by mass or more and 95% by mass or less. This is because if the blending amount of the silica powder is too small, it is difficult to obtain effects such as improving the strength of the encapsulating material and suppressing thermal expansion, and conversely, if it is too large, it is related to the surface treatment of the silica powder. This is because segregation due to aggregation of silica powder is likely to occur in the composite material, and the viscosity of the composite material becomes too large, which makes it difficult to put it into practical use as a sealing material.

As the silane coupling agent, a known coupling agent may be used, but one having an epoxy-based functional group is preferable.

The present invention will be described through the following examples and comparative examples. However, the present invention is not construed as being limited to the following examples.

(Examples 1 to 3)
Amorphous silica particles containing calcium were prepared by thermal spraying. Lithium carbonate particles were mixed with the spherical amorphous silica particles, filled in an alumina container, and heat-treated in an air atmosphere (atmospheric pressure) using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.). The mixing amount of lithium carbonate is 0.25% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium in terms of oxide, and calcium contained in the amorphous silica particles. Was 0.004% by mass in terms of oxide. The temperature was raised to 900 ° C. (Example 1), 1000 ° C. (Example 2), and 1100 ° C. (Example 3) at a heating rate of 300 ° C./hour, and held for 6 hours. Then, the temperature was cooled to room temperature at a temperature lowering rate of about 100 ° C./hour.

(Examples 4 to 6)
Amorphous silica particles containing calcium were prepared by thermal spraying. The amount of calcium contained in the amorphous silica particles was 0.0040% by mass. 0.10% by mass (Example 4) and 0.07% by mass (Example 4) of lithium carbonate in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide. 5), 0.05% by mass (Example 6) were mixed. The heating rate was 300 ° C./hour, the temperature was raised to 930 ° C. (Example 4), 1030 ° C. (Example 5), and 1130 ° C. (Example 6), and the temperature was maintained for 6 hours. Then, it was cooled to room temperature at a heating rate of 100 ° C./hour.

(Examples 7 to 9)
Amorphous silica particles containing calcium were prepared by thermal spraying. 0.25% by mass of lithium carbonate particles in terms of oxide is mixed with the total mass of the mass of spherical amorphous silica and the mass of lithium in terms of oxide, and the calcium contained in the amorphous silica particles is It was 0.24% by mass in terms of oxide. The temperature was raised to 900 ° C. (Example 7), 1000 ° C. (Example 8), and 1100 ° C. (Example 9) at a heating rate of 300 ° C./hour, and held for 6 hours. Except for the above, the heat treatment was performed in the same manner as in Example 1.

(Example 10 to Example 12)
Amorphous silica particles containing calcium were prepared by thermal spraying. 0.25% by mass of lithium carbonate particles in terms of oxide is mixed with the total mass of the mass of spherical amorphous silica and the mass of lithium in terms of oxide, and calcium contained in the amorphous silica particles is mixed. Was 0.66% by mass in terms of oxide. Then, the temperature was raised to 900 ° C. (Example 10), 1000 ° C. (Example 11), and 1100 ° C. (Example 12) at a heating rate of 300 ° C./hour, and held for 6 hours. Then, the temperature was cooled to room temperature at a temperature lowering rate of about 100 ° C./hour.

(Example 13, Example 14)
Amorphous silica particles containing calcium were prepared by thermal spraying. Calcium contained in the amorphous silica particles by mixing 0.05% by mass of lithium carbonate particles in terms of oxide with the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide. Was 0.66% by mass in terms of oxide. After that, the temperature was raised to 925 ° C. in Example 13 and to 1080 ° C. in Example 14 at a heating rate of 300 ° C./hour. Then, the heat treatment was carried out in the same manner as in Example 1 except that it was held for 6 hours in Example 13 and for 24 hours in Example 14.

(Example 15, Example 16)
Amorphous silica particles containing calcium were prepared by thermal spraying. 0.10% by mass (Example 15) and 0.02% by mass (implementation) of lithium carbonate particles in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide. Example 16) After mixing, the amount of calcium contained in the amorphous silica particles was 0.66% by mass in terms of oxide. After that, the temperature was raised to 925 ° C. in Example 15 and to 950 ° C. in Example 16 at a heating rate of 300 ° C./hour. After that, heat treatment was performed in the same manner as in Example 1 except that the mixture was held for 6 hours.

(Examples 17 to 20)
Amorphous silica particles were prepared by thermal spraying. After mixing calcium hydroxide particles and lithium carbonate particles with the spherical amorphous silica particles, the particles are filled in an alumina container and used in an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) under an atmospheric atmosphere (atmospheric pressure). ) Was heat-treated. The mixing amount of calcium hydroxide is 0.48% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica, the mass of calcium converted to oxide, and the mass of lithium converted to oxide. The mixing amount of lithium was 0.04% by mass (Example 17), 0.06% by mass (Example 18), 0.08% by mass (Example 19), and 0.10% by mass (implementation) in terms of oxides. Example 20). The heating rate was 300 ° C./hour, the temperature was raised to 925 ° C., and the temperature was maintained for 12 hours. Then, the temperature was cooled to room temperature at a temperature lowering rate of about 100 ° C./hour.

(Example 21, Example 22)
Amorphous silica particles containing calcium and lithium were prepared by thermal spraying. The spherical amorphous silica particles were filled in an alumina container and heat-treated in an atmospheric atmosphere (atmospheric pressure) using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.). Calcium contained in the amorphous silica particles was 0.82% by mass in terms of oxide, and lithium was 0.08% by mass in terms of oxide. The temperature was raised to 950 ° C. (Example 21) and 1050 ° C. (Example 22) at a rate of temperature rise of 300 ° C./hour, and maintained for 24 hours. Then, the temperature was cooled to room temperature at a temperature lowering rate of about 100 ° C./hour.

In addition, amorphous silica particles containing lithium were produced by thermal spraying. After mixing the calcium compound particles with the spherical amorphous silica particles, the spherical amorphous silica particles are filled in an alumina container and used in an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) to create an atmospheric atmosphere. The heat treatment was performed in the range of 850 ° C to 1150 ° C under the pressure (atmosphere).

(Comparative Example 1)
Amorphous silica particles containing 0.004% by mass of calcium in terms of oxide were prepared by thermal spraying. The heat treatment was performed in the same manner as in Example 1 except that the lithium carbonate particles were not mixed with the spherical amorphous silica particles, and then the temperature was raised to 900 ° C. at 300 ° C./hour and held for 6 hours. went.

(Comparative Example 2)
Amorphous silica particles containing calcium were prepared by thermal spraying. Lithium carbonate particles are mixed at 0.25% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide, and the calcium contained in the amorphous silica particles is oxidized. The temperature was set to 0.004% by mass in terms of physical substances, and then the temperature was raised to 1200 ° C. at 300 ° C./hour, and heat treatment was performed in the same manner as in Example 1 except that the temperature was maintained for 6 hours.

(Comparative Example 3, Comparative Example 4)
Amorphous silica particles containing calcium were prepared by thermal spraying. Lithium carbonate particles are mixed at 0.25% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide, and the calcium contained in the amorphous silica particles is oxidized. The temperature was set to 0.24% by mass in terms of physical substances, and then the temperature was raised to 1200 ° C. (Comparative Example 3) and 800 ° C. (Comparative Example 4) at 300 ° C./hour, and the temperature was maintained for 6 hours. The heat treatment was performed in the same manner as in 1.

(Comparative Example 5)
Amorphous silica particles containing calcium were prepared by thermal spraying. Lithium carbonate particles are mixed at 0.25% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide, and the calcium contained in the amorphous silica particles is oxidized. The temperature was set to 0.0014% by mass in terms of physical substances, and then the temperature was raised to 900 ° C. at 300 ° C./hour, and heat treatment was performed in the same manner as in Example 1 except that the temperature was maintained for 6 hours.

(Comparative Example 6)
Amorphous silica particles containing calcium were prepared by thermal spraying. Lithium carbonate particles are mixed in an oxide equivalent of 0.01% by mass with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium converted to oxide, and the calcium contained in the amorphous silica particles is oxidized. The temperature was set to 0.66% by mass in terms of physical substances, and then the temperature was raised to 925 ° C. at 300 ° C./hour, and heat treatment was performed in the same manner as in Example 1 except that the temperature was maintained for 6 hours.

(Comparative Example 7)
Amorphous silica particles containing 0.66% by mass of calcium in terms of metal were prepared by thermal spraying. The heat treatment was performed in the same manner as in Example 1 except that the lithium carbonate particles were not mixed with the spherical amorphous silica particles, and then the temperature was raised to 1100 ° C. at 300 ° C./hour and held for 6 hours. went.

The abundance ratio of amorphous and crystalline silica of the silica particles obtained by heat treatment, the type of crystalline silica, and the ratio thereof were determined by XRD. In the present invention, an X-ray diffractometer "D2 PHASER" (manufactured by Bruker) was used. Quantitative analysis of the crystal phase by the Rietveld method was performed by the crystal structure analysis software "TOPAS" (manufactured by Bruker).

The circularity was determined by the flow type particle image analysis method. In the present invention, a flow type particle image analyzer "FPIA-3000" (manufactured by Spectris) was used.

The content of impurity elements such as lithium and calcium in the spherical silica particles of the present invention was measured by ICP mass spectrometry (ICP-MS). Specifically, it was measured using ICP-MS (“7700X” manufactured by Agilent) in accordance with JIS-K0133. An aqueous solution in which silica particles were completely dissolved with hydrofluoric acid was used as a sample. Here, the content of the impurity element contained in the silica particles was defined as the content of the impurity element in the silica solution. For the calibration curve, a base solution containing only reagents was used.

The average particle size (D50) of the spherical quartz particles was measured by a laser diffraction / scattering type particle size distribution measuring method. In the present invention, a laser diffraction / scattering type particle size distribution measuring device "CILAS920" (manufactured by Cyrus) was used.

In all of the spherical crystalline silica particles obtained in the examples according to the present invention, the lithium content is in the range of 0.02% by mass or more and less than 0.40% by mass in terms of oxide, and the phase of crystalline silica is used. The ratio of the crystalline silica phase to the spherical crystalline silica particles was 40.0% or more, and the proportion of quartz in the crystalline silica phase was 80% by mass or more. The spherical crystalline silica particles of the examples according to the present invention had a circularity of 0.83 to 0.95.
The average particle size of the spherical amorphous silica particles containing 0.004% by mass of calcium in terms of oxide was 35.1 μm, whereas the spherical crystalline silica particles of the present invention using this raw material had an average particle size of 35.1 μm. , 35.2 μm to 35.6 μm.
The average particle size of the spherical amorphous silica particles containing 0.24% by mass of calcium was 33.8 μm, whereas the spherical crystalline silica particles of the present invention using this raw material had an average particle size of 33.3 μm or more. It was 33.9 μm.
Furthermore, the spherical amorphous silica particles containing 0.66% by mass of calcium in terms of oxide were 41.1 μm, whereas the spherical crystalline silica particles of the present invention using this raw material were 40. It was 9 μm to 41.5 μm.
Further, a mixture obtained by mixing a calcium raw material containing 0.48% by mass of calcium in terms of oxide and a lithium raw material containing 0.04 to 0.10% by mass of lithium in terms of oxide with amorphous silica particles. When the raw material powder was heat-treated, the average particle size of the spherical amorphous silica particles was 32.3 μm, whereas the spherical crystalline silica particles of the present invention using this mixed raw material powder had 31. It was 6 μm to 35.1 μm.
Further, in the spherical amorphous silica particles containing 0.82% by mass and 0.08% by mass, respectively, of calcium and lithium in terms of oxide, the average particle size was 21.5 μm, whereas this raw material. The spherical crystalline silica particles of the present invention using the above were 20.3 μm and 21.9 μm.

Comparing Example 1 and Example 7 with Comparative Example 5, even if the lithium content is the same 0.25% by mass, the calcium content exceeds 0.004% by mass in terms of oxide only in the spherical crystalline silica particles. It can be seen that the ratio of the phase of crystalline silica exceeds 40.0%. It can be seen that the synergistic effect of the coexistence of calcium and the lithium element is exhibited and crystallization is promoted. Further, looking at Comparative Example 1, even if calcium is contained in an oxide equivalent of 0.004% by mass, crystallization does not proceed unless lithium is added. It can be seen that the coexistence of lithium and calcium is necessary.

Comparing Examples 4 to 6, Examples 13 to 16 with Comparative Example 6 and Comparative Example 7, it can be seen that the lower limit of the amount of lithium added is 0.02% by mass.

Example 1 to Example 3 and Comparative Example 2 Further, comparing Example 7 to Example 9 and Comparative Example 3, the cristobalite content increases when the heat treatment temperature becomes high, and in the phase of crystalline silica at 1200 ° C. It can be seen that the proportion of quartz is less than 80% by mass. Further, comparing Examples 7 to 9 with Comparative Example 4, crystallization does not proceed at a heat treatment temperature of 800 ° C., and the ratio of the phase of crystalline silica in the spherical crystalline silica particles is less than 40%. I understand. The preferred heat treatment temperature is 850 ° C to 1150 ° C. A more preferable temperature range is 875 ° C to 1100 ° C.

Comparing Example 12 and Comparative Example 7, even if calcium is contained in an oxide equivalent of 0.66% by mass or more, when the amount of lithium added is not added, the phase of crystalline silica in the spherical crystalline silica particles is the same. The ratio is 11.4%, which is less than 40.0%. When lithium is 0.02% by mass or more in terms of oxide, the ratio of the crystalline silica phase in the spherical crystalline silica particles exceeds 40%, and the ratio of quartz to the crystalline silica phase exceeds 80% by mass. .. It was found that this high quartz crystallization rate is a synergistic effect due to the coexistence of calcium and lithium. Even if the content of lithium or calcium is increased (0.02% by mass or more in terms of lithium oxide, 0.004% or more in terms of calcium oxide), there is no problem in the degree of crystallization and the degree of quartzification, and it is spherical. The ratio of the crystalline silica phase to the crystalline silica particles was 40.0% or more, and the ratio of quartz to the crystalline silica phase exceeded 80% by mass.

The zinc content of the spherical crystalline silica particles used in the examples and comparative examples of the present invention is less than 1.0 ppm in terms of metal content, and the total of alkali metals (K and Na) other than lithium is a metal. In terms of conversion, the total amount of alkaline earth metals (Mg + Ba) other than calcium was 1.8 to 42 ppm, and that of aluminum metal was 90 to 4552 ppm. These metal impurities other than lithium and calcium may be contained in silica as long as they do not affect crystallization.

The spherical crystalline silica particles of the present invention are not limited to the semiconductor encapsulating material, and can be used for other purposes. Specifically, it can also be used as a prepreg for printed circuit boards, various engineering plastics, and the like.

Claims

The circularity is 0.80 or more, lithium is contained in an oxide equivalent of 0.02% by mass or more and less than 0.40% by mass, and calcium is contained in an oxide equivalent of 0.004% by mass or more and less than 1.0% by mass. The spherical crystalline silica particles containing the crystalline silica phase, wherein the ratio of the crystalline silica phase to the spherical crystalline silica particles is 40.0% or more, and the crystalline silica is contained. Spherical crystalline silica particles in which the proportion of quartz in the phase is 80.0% by mass or more.
The spherical crystalline silica particles according to claim 1, wherein the ratio of the crystalline silica phase is 70.0% or more, and the ratio of quartz to the crystalline silica phase is 85.0% by mass or more. ..
The spherical crystalline silica particles according to claim 2, wherein the ratio of the crystalline silica phase is 80.0% or more, and the ratio of quartz to the crystalline silica phase is 90.0% by mass or more. ..
The spherical crystalline silica particles according to any one of claims 1 to 3, wherein the average particle size (D50) is 3 to 100 μm.
The method for producing spherical crystalline silica particles according to any one of claims 1 to 4.
Spherical crystalline material comprising heat-treating a mixed raw material powder obtained by mixing a calcium raw material and a lithium raw material with spherical amorphous silica particles having a circularity of 0.80 or more at 850 ° C to 1150 ° C. Method for producing silica particles.
The method for producing spherical crystalline silica particles according to any one of claims 1 to 4.
It comprises heat-treating a mixed raw material powder obtained by mixing a lithium raw material with spherical amorphous silica particles having a circularity of 0.80 or more and containing a calcium component at 850 ° C to 1150 ° C. A method for producing spherical crystalline silica particles.
The method for producing spherical crystalline silica particles according to any one of claims 1 to 4.
The present invention comprises heat-treating a mixed raw material powder obtained by mixing a calcium raw material with spherical amorphous silica particles having a circularity of 0.80 or more and containing a lithium component at 850 ° C to 1150 ° C. A method for producing spherical crystalline silica particles.
The method for producing spherical crystalline silica particles according to any one of claims 1 to 4.
A method for producing spherical crystalline silica particles, which comprises heat-treating spherical amorphous silica particles having a circularity of 0.80 or more and containing a calcium component and a lithium component at 850 ° C to 1150 ° C.
The method for producing spherical crystalline silica particles according to any one of claims 5 to 8, wherein the heat treatment temperature is 875 ° C to 1110 ° C.