Sheet-like resin composition

Abstract

To provide a sheet-like resin composition that is less prone to malfunctions caused by alpha radiation and has good sealing properties. [Solution] The solution comprises alumina particles and epoxy resin, wherein the alumina particles have a particle diameter D50 of 50% of the cumulative particle size distribution from the finest particle side based on volume, which is 10 μm or less, a thickness of 0.13 mm or more and 1.00 mm or less, and an α dose of 0.05 cph / cm². 2 The following is a sheet-like resin composition.

Description

[Technical Field]

[0001] This disclosure relates to a sheet-like resin composition. [Background technology]

[0002] The heat generated when an electric current is passed through an electronic component can easily adversely affect its performance, so it is desirable that the heat be dissipated quickly. Therefore, for example, the sealing member that encloses an IC chip incorporated into an electronic component should be made from a material that exhibits high thermal conductivity for heat dissipation. Generally, sealing members can be made from a resin composition containing alumina particles and resin, as described in Patent Documents 1 to 3.

[0003] Furthermore, IC chips made of semiconductor materials are susceptible to the effects of alpha radiation, and malfunctions (soft errors) caused by alpha radiation are a problem. Patent documents 1 to 3 propose using alumina particles with extremely limited uranium and thorium content in order to reduce the amount of alpha radiation in the sealing material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-110146 [Patent Document 2] International Publication No. 2022 / 102697 [Patent Document 3] Japanese Patent Publication No. 2014-5359 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In recent years, with the miniaturization of IC chips and the narrowing of wiring pitches, IC chips have become even more susceptible to the effects of alpha radiation. Therefore, resin compositions used in semiconductor encapsulation materials are required to reduce malfunctions caused by alpha radiation more effectively than ever before.

[0006] Furthermore, in order to improve the functionality of electronic components, electronic components (panel-level packages: PLPs) composed of multiple IC chips mounted on a substrate have been proposed. In the general manufacturing method of PLPs, after mounting multiple IC chips on a substrate, the multiple IC chips are encapsulated together with a liquid resin composition. In recent years, in order to increase the number of chips that can be mounted, the surface area of ​​the substrate has been increasing. Since it is difficult to encapsulate large-area substrates with a uniform thickness using liquid resin compositions, the use of sheet-shaped resin compositions, which are pre-formed into sheets of uniform thickness, is being considered as an alternative to liquid resin compositions.

[0007] However, since sheet-type resin compositions are used in a solid state, they have lower fluidity compared to liquid resin compositions. Therefore, sheet-type resin compositions may have lower sealing properties (the ability to seal so that the IC chip is not exposed and the surface is flat) compared to liquid resin compositions.

[0008] To meet all these requirements, a sheet-like resin composition that can reduce malfunctions caused by alpha radiation and has good sealing properties is desired. However, Patent Documents 1 to 3 have not examined a sheet-like resin composition that satisfies all of these requirements. In light of these circumstances, the object of one embodiment of the present invention is to provide a sheet-like resin composition that is less prone to malfunctions caused by alpha rays and has good sealing properties. [Means for solving the problem]

[0009] One aspect of the present invention is: It contains alumina particles and epoxy resin. The alumina particles have a particle diameter D50 of 10 μm or less at the cumulative 50% from the finest particle side of the volume-based cumulative particle size distribution. The thickness is between 0.13 mm and 1.00 mm. Alpha dose: 0.05 cph / cm² 2 The following is a sheet-like resin composition.

[0010] Aspect 2 of the present invention is, The sheet-like resin composition according to Embodiment 1, wherein the D50 of the alumina particles is less than 6.0 μm.

[0011] Embodiment 3 of the present invention is The sheet-like resin composition according to Embodiment 1 or 2, wherein the thickness is 0.90 mm or less.

[0012] Embodiment 4 of the present invention is The sheet-like resin composition according to any one of Embodiments 1 to 3, wherein the average circularity of the alumina particles is 0.85 or more.

[0013] Embodiment 5 of the present invention is The sheet-like resin composition according to any one of Embodiments 1 to 4, further containing a solvent.

[0014] Embodiment 6 of the present invention is The sheet-like resin composition according to Embodiment 5, wherein the ratio of the mass of the alumina particles to the solid content of the sheet-like resin composition is 95% by mass or less.

[0015] Embodiment 7 of the present invention is The sheet-like resin composition according to Embodiment 5 or 6, wherein the ratio of the mass of the alumina particles to the solid content of the sheet-like resin composition is 50% by mass or more.

Advantages of the Invention

[0016] According to one embodiment of the present invention, it is possible to provide a sheet-like resin composition in which malfunction due to α-rays is unlikely to occur and the sealing property is good.

Modes for Carrying Out the Invention

[0017] The present inventor conducted intensive studies for the purpose of providing a sheet-like resin composition capable of achieving both suppression of malfunction due to α-rays and good sealing properties. As a result, it contains alumina particles having a particle diameter D50 of 10 μm or less and an epoxy resin, has a thickness of 0.13 mm or more and 1.00 mm or less, and an α-ray dose of 0.05 cph / cm 2We found that the above objective can be achieved with a sheet-like resin composition that satisfies the following requirements.

[0018] Alumina particles with low alpha radiation doses and small particle sizes tend to aggregate and settle in sheet-like compositions, which can lead to poor sealing performance. However, in the embodiments of the present invention, this problem can be solved by controlling the thickness of the sheet-like resin composition.

[0019] The sheet-like resin composition according to the embodiment will be described below.

[0020] [Sheet-like resin composition] The sheet-like resin composition according to this embodiment contains alumina particles and epoxy resin. The α-dose of the sheet-like resin composition is 0.05 cph / cm². 2 The following limitations apply. This makes it possible to suppress malfunctions of IC chips due to alpha radiation when the sheet-like resin composition is used as a sealing material for IC chips. The alpha dose of the sheet-like resin composition is preferably 0.020 cph / cm². 2 More preferably, 0.005 cph / cm 2 The following is particularly preferred: 0.002 cph / cm 2 The following applies: The lower limit of the α-dose for the sheet-like resin composition is not particularly limited, but for example, 0.001 cph / cm². 2 That is the case.

[0021] The alpha radiation source in sheet-like resin compositions is primarily the radioactive elements contained in alumina particles. Therefore, reducing the amount of radioactive elements in the alumina particles is effective in suppressing the alpha radiation dose from sheet-like resin compositions. The suitable range of radioactive element content in alumina particles will be described later. Furthermore, while it is possible to suppress the alpha radiation dose of the sheet-like resin composition by reducing the amount of alumina particles contained in the sheet-like resin composition (alumina filling rate), this is undesirable because it may reduce the sealing properties of the sheet-like resin composition or reduce its thermal conductivity, thereby reducing its heat dissipation capabilities.

[0022] The "sheet-like resin composition" in the present invention is a sheet-like resin composition containing alumina particles and epoxy resin, which has fluidity when heated and pressurized. The sheet-like resin composition includes, for example, an uncured sheet-like resin composition (also called a Stage A sheet-like resin composition) and a sheet-like resin composition obtained by partially curing an uncured sheet-like resin composition (also called a Stage B resin composition). If the sheet-like resin composition contains a solvent, for example, an uncured (Stage A) sheet-like resin composition can be obtained by applying a liquid resin composition in a sheet-like manner to a substrate, and then removing part of the solvent by evaporation or the like. Furthermore, as will be described later, a Stage B sheet-like resin composition can be obtained by partially curing the resin by further removing the solvent from the uncured (Stage A) sheet-like resin composition.

[0023] In one embodiment of the present invention, the sheet-like resin composition contains a solvent. When the sheet-like resin composition contains a solvent, it flows easily, can be easily deformed to conform to the fine structure of the IC chip and substrate, and can seal a dense structure without gaps. The solvent can be any known solvent, and is not limited as long as it can dissolve epoxy resin, but examples include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, amine-based solvents, amide-based solvents, halogen-based solvents, hydrocarbon-based solvents, nitrile-based solvents, etc. From the viewpoint of being a good solvent for epoxy resin and having excellent coatability of the resulting resin composition, ketone-based solvents and ester-based solvents are preferred for the resin composition.

[0024] Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone. Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, n-propyl acetate, amine acetate, and sec-butyl acetate. The sheet-like resin composition preferably contains one or more selected from the group consisting of methyl ethyl ketone, cyclopentanone, and cyclohexanone.

[0025] The amount of solvent in the uncured sheet-like resin composition and the semi-cured sheet-like resin composition is preferably 0.001% by mass or more, and preferably 10% by mass or less, relative to the total mass of the sheet-like resin composition. When the amount of solvent is within the above range, the fluidity during heating and pressurizing is good, and aggregation and sedimentation of alumina particles are prevented, making it easier to improve sealing performance.

[0026] A semi-cured sheet-like resin composition can be produced, for example, by further drying an uncured sheet-like resin composition, reducing the amount of solvent by heating and pressurizing, or by reacting it with an epoxy resin. In the present invention, the amount of solvent in the semi-cured sheet-like resin composition is less than the amount of solvent in the uncured sheet-like resin composition. The amount of solvent in the sheet-like resin composition can be determined, for example, from the change in mass of the sheet-like resin composition before and after heating such as drying, and specifically by the method described in the examples below.

[0027] The sheet-like resin composition according to this embodiment has a thickness of 0.13 mm or more and 1.00 mm or less. A thickness of 0.13 mm or more can suppress the partial exposure of the IC chip and the occurrence of surface irregularities when encapsulating the IC chip. A thickness of 1.00 mm or less can reduce the heating time required for sufficient curing and allow for a composition in which alumina particles are uniformly dispersed. The thickness is preferably 0.90 mm or less, more preferably 0.75 mm or less, even more preferably 0.60 mm or less, even more preferably 0.50 mm or less, particularly preferably 0.40 mm or less, preferably 0.15 mm or more, more preferably 0.16 mm or more, even more preferably 0.20 mm or more, particularly preferably more than 0.20 mm, and particularly even more preferably 0.25 mm or more. When the thickness of the sheet-like resin composition is within the above range, the alumina particles (especially particles with small particle sizes) and epoxy resin flow uniformly when heated and pressurized, and voids are less likely to occur after encapsulation and curing. Furthermore, when the sheet-like resin composition is stored in the atmosphere, aggregation and sedimentation of alumina particles (especially small particles) due to evaporation of solvents from the surface are less likely to occur, and the sealing properties are easily maintained over a long period of time.

[0028] The ratio of the mass of alumina particles to the solid content of the sheet-like resin composition (also referred to as the "alumina filling rate") is preferably 95% by mass or less. This makes it possible to obtain a sheet-like resin composition with good sealing properties. From the viewpoint of further improving the sealing properties of the sheet-like resin composition, the alumina filling rate is more preferably 92% by mass or less, even more preferably 90% by mass or less, even more preferably 88% by mass or less, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, if the alumina filling rate is above the lower limit mentioned above, the thermal conductivity of the cured product of the sheet-like resin composition can be improved.

[0029] In this invention, the solid content of the sheet-like resin composition refers to the solid content that remains when the sheet-like resin composition is heated, excluding components that evaporate or volatilize upon heating, such as the solvent mentioned above. Even components that are liquid at 25°C are included in the solid content if they are incorporated into the solid content of the sheet-like resin composition upon heating.

[0030] The alumina packing ratio can be determined, for example, by the following method: First, the volatile components such as solvents are removed by heating, and then the mass of the sheet-like resin composition (corresponding to the mass of "solids") is measured. Next, the epoxy resin and other components contained in the sheet-like resin composition are removed by, for example, dissolving them in an organic solvent or thermal decomposing them by heating to a temperature of 500°C or higher, separating only the alumina particles, and the mass of these alumina particles is measured. The alumina packing ratio can then be calculated using these measurement results. Alternatively, the alumina packing ratio can also be calculated from the amount of sheet-like resin composition used.

[0031] Next, the alumina particles and epoxy resin that constitute the sheet-like resin composition will be described in detail.

[0032] [Alumina particles] The alumina particles according to this embodiment have the following characteristics.

[0033] (Particle size of alumina particles) The alumina particles have a particle size D50 of 10 μm or less at the 50% cumulative particle size distribution from the finest particle side based on volume. Normally, if the particle size of alumina particles is small, aggregation occurs and they tend to settle in the sheet-like resin composition, which can lead to poor sealing performance. However, according to the present invention, good sealing performance can be achieved even if the particle size D50 of the alumina particles is 10 μm or less. In the present invention, the D50 of the alumina particles is preferably less than 6.0 μm, more preferably 5.5 μm or less, even more preferably 5.0 μm or less, even more preferably 4.0 μm or less, particularly preferably 3.0 μm or less, preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 1.8 μm or more, and particularly preferably 2.0 μm or more. When the D50 of the alumina particles in the present invention is within the above range, good dispersibility in epoxy resin can be achieved, and sealing performance can be further enhanced.

[0034] The particle size D50 of alumina particles can be determined, for example, by measuring the particle size distribution of alumina particles using the laser diffraction method with a Microtrac MT3300EXII laser particle size distribution analyzer manufactured by Microtrac-Bell Co., Ltd. The particle size of alumina particles in a sheet-like resin composition can be measured by removing the epoxy resin and other components contained in the sheet-like resin composition, for example, by dissolving them in an organic solvent or by thermal decomposition by heating them to a temperature of 500°C or higher, separating only the alumina particles, and then using those alumina particles.

[0035] (Average roundness of alumina particles) The average roundness of the alumina particles is preferably 0.85 or higher, more preferably 0.88 or higher, even more preferably 0.90 or higher, and particularly preferably 0.93 or higher, and is usually 1.00 or lower, preferably 0.99 or lower, and more preferably 0.98 or lower. When the average roundness of the alumina particles is within the above range, it is easier to increase the filling rate of the alumina particles into the epoxy resin, and sedimentation in the resin composition is less likely to occur, improving dispersibility and thus achieving good sealing performance. In particular, when the thickness of the sheet-like resin sealant is within the above range, the alumina particles (especially particles with small particle sizes) and the epoxy resin flow more uniformly when heated and pressurized, and voids are less likely to occur after curing. Furthermore, a high average roundness of the alumina particles also improves the kneadability with the epoxy resin, which has the effect of increasing the fluidity of the liquid resin composition after kneading and making it easier to mold into a sheet.

[0036] The roundness (SPHT) can be analyzed according to ISO 9276-6. SPHT = 4πA / P 2 The average roundness of alumina particles is determined from the following equation. In the equation, A is the measured area of ​​the projected particle image, and P is the measured perimeter of the particle projection image. The average roundness of alumina particles is measured using a measuring device based on the principle of dynamic image analysis in accordance with ISO 13322-2 (e.g., CAMSIZER X2 (manufactured by VERDER Scientific)). The average roundness of alumina particles in a sheet-like resin composition can be measured by removing the epoxy resin and other components contained in the sheet-like resin composition, for example, by dissolving them in an organic solvent or by thermal decomposition by heating them to a temperature of 500°C or higher, separating only the alumina particles, and then using those alumina particles.

[0037] Another method for determining the average roundness of alumina particles is to use image analysis. For a sheet-like resin composition, cross-sectional observation can be performed using a scanning electron microscope (SEM), and all alumina particles contained within a predetermined observation area (e.g., 200 μm × 200 μm) can be image-analyzed. Based on the measurement results of their roundness, the average roundness can be calculated.

[0038] (Uranium and thorium content of alumina particles) As described above, by reducing the radioactive elements contained in the alumina particles, the alpha dose of the sheet-shaped resin composition can be brought within a predetermined range. In the case of a sheet-shaped resin composition in which the alumina filling rate is in a general range (for example, 20% by mass to 99% by mass), in order to make the alpha dose of the sheet-shaped resin composition 0.050 cph / cm 2 or less as follows, it is preferable that the uranium content is, for example, 550 ppb or less and the thorium content is, for example, 10 ppb or less. By suppressing the uranium content and the thorium content of the alumina particles to extremely small amounts as described above, the alpha dose emitted from the alumina particles can be reduced, and as a result, the alpha dose emitted from the sheet-shaped resin composition can be suppressed.

[0039] The uranium content is preferably 300 ppb or less, more preferably 100 ppb or less, still more preferably 50 ppb or less, particularly preferably 30 ppb or less, and is, for example, 10 ppb or less, or 5 ppb or less. The lower limit of the uranium content is not particularly limited, but it may be 0.1 ppb or more. The thorium content is preferably 8 ppb or less, more preferably 5 ppb or less, and particularly preferably 2 ppb or less. The lower limit of the thorium content is not particularly limited, but it may be 0.1 ppb or more. The uranium content and the thorium content of the alumina particles can be measured by inductively coupled plasma mass spectrometry (ICP-MS method).

[0040] [Epoxy resin] In this embodiment, the sheet-like resin composition contains an epoxy resin. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol AP type epoxy resin, bisphenol AF type epoxy resin, bisphenol B type epoxy resin, bisphenol BP type epoxy resin, bisphenol C type epoxy resin, bisphenol E type epoxy resin, bisphenol F type epoxy resin, bisphenol G type epoxy resin, bisphenol M type epoxy resin, bisphenol S type epoxy resin, bisphenol P type epoxy resin, bisphenol PH type epoxy resin, bisphenol TMC type epoxy resin, bisphenol Z type epoxy resin, bisphenol S type epoxy resin such as hexanediol bisphenol S diglycidyl ether, novolacphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, bixylenol type epoxy resin such as bixylenol diglycidyl ether, hydrogenated bisphenol A type epoxy resin such as hydrogenated bisphenol A glycidyl ether, and dibasic acid modified diglycidyl ether type epoxy resins thereof, aliphatic epoxy resins, and phenylcyclohexyl type epoxy resins. Preferred epoxy resins include aromatic epoxy resins, such as phenylcyclohexyl epoxy resins, naphthalene epoxy resins, phenolic epoxy resins, biphenyl epoxy resins, and bisphenol A epoxy resins. From the viewpoint of thermal conductivity, epoxy resins having mesogenic groups (sometimes called mesogenic epoxy resins) are more preferred among these, and epoxy resins having mesogenic groups that exhibit a phase transition temperature in the temperature range of 100°C to 200°C during sealing and exhibit liquid crystalline properties are even more preferred. The sheet-like resin composition may contain one or more aromatic epoxy resins. In other words, the sheet-like resin composition may contain one or more aromatic epoxy resins selected from the group consisting of phenylcyclohexyl epoxy resins, naphthalene epoxy resins, phenolic epoxy resins, biphenyl epoxy resins, and bisphenol A epoxy resins. These resins are expected to have the effect of shielding α rays emitted from alumina particles.Furthermore, because aromatic epoxy resins have high dimensional stability against external energy such as heat, it is easy to obtain sheet-like resin compositions that can form cured products with minimal surface unevenness.

[0041] The sheet-like resin composition may optionally contain, either alone or in combination of two or more known additives, such as plasticizers, curing agents, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weathering agents, antiblocking agents, antistatic agents, leveling agents, and mold release agents, as long as they do not impair the effects of the invention. As an example of a preferred embodiment of the present invention, the sheet-like resin composition comprises alumina particles, epoxy resin, solvent, and curing agent. Examples of curing agents include amine-based curing agents such as 4,4-diaminodiphenylmethane.

[0042] [Method for producing sheet-like resin compositions] A method for producing a sheet-like resin composition will be described. A sheet-like resin composition can be obtained by mixing the alumina particles according to this embodiment with an epoxy resin using a commonly used and known method, and then molding the mixture into a sheet. The mixing method is not particularly limited, and mills, mixers, stirring blades, etc., can be used. In addition to alumina particles and epoxy resin, known additives such as plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weathering agents, antiblocking agents, antistatic agents, leveling agents, and mold release agents may be mixed together, either alone or in combination of two or more, as long as they do not impair the effects of the invention.

[0043] One example of a method for producing a sheet-like resin composition is to mix epoxy resin, alumina particles, a solvent, and a curing agent, then apply the resulting mixture to a substrate, and remove part of the solvent by drying or other means to obtain a sheet-like resin composition (uncured). For example, by further reducing the amount of solvent by heating and pressurizing, a semi-cured sheet-like resin composition can be obtained. The method of applying the mixture is not particularly limited, but coating equipment such as a comma coater, lip coater, roll coater, gravure coater, die coater, or spin coater can be used. A known curing agent can be used, and known methods can be employed for mixing and curing.

[0044] [Method for producing alumina particles] The alumina particles used in this embodiment can be manufactured, for example, by the method shown below.

[0045] (raw material: alumina) The raw material alumina is produced by known methods. Examples include the Bayer process, ammonium alum process, ammonium aluminum carbonate hydroxide process (AACH process), solvent extraction, organoaluminum hydrolysis (aluminum alkoxide process), CZ process, Bernoulli process, Chiroporus process, Bridgman process, EFG process, and other melt growth methods.

[0046] In the Bayer process, raw alumina can be produced by calcining aluminum hydroxide obtained from bauxite. Furthermore, the ammonium alum method, AACH method, solvent extraction method, and aluminum alkoxide method are preferable because they allow for the production of high-purity raw alumina with low uranium and thorium content. Using raw alumina produced by these methods, with a uranium content of, for example, 550 ppb or less and a thorium content of, for example, 150 ppb or less, in the production of alumina particles is preferable because it yields alumina particles with reduced uranium and thorium content. Moreover, from the viewpoint of further reducing uranium and thorium content, it is even more preferable to refine metallic aluminum to a purity of 99.999% by mass or higher, produce aluminum hydroxide from that metallic aluminum, and then form alumina. The uranium content is preferably 500 ppb or less, more preferably 200 ppb or less, and even more preferably 10 ppb or less. Furthermore, the thorium content is preferably 100 ppb or less, more preferably 50 ppb or less, even more preferably 20 ppb or less, and particularly preferably 10 ppb or less.

[0047] (Crushing of raw material alumina) To easily obtain alumina particles of a desired size by the flame melting method, raw alumina is crushed to obtain alumina raw material powder for flame melting. The raw alumina can be crushed using known methods such as a vibratory mill, bead mill, ball mill, or jet mill, and may be crushed in either a dry or wet state.

[0048] In the above grinding process, a surface protectant may be used. The surface protectant not only protects the surface of the alumina raw material powder after grinding, but may also have the function of inactivating the surface of the alumina raw material powder. Because the surface protectant reduces aggregation of alumina raw material powders due to its surface inactivation function, it is suitable for obtaining alumina particles of a target particle size after flame melting using raw material alumina with a high BET specific surface area that is prone to aggregation. Suitable surface protectants include, for example, monohydric alcohols such as methanol, ethanol, 1-propanol, and 2-propanol; glycols such as ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol; amines such as triethanolamine; and higher fatty acids such as palmitic acid, stearic acid, and oleic acid. One of these surface protectants may be used alone, or two or more may be used in combination. Of these, glycols are preferred, and in particular, one or more of ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol are preferred.

[0049] Polyethylene glycol and polypropylene glycol, which are preferably used as surface protective agents, do not have any particular restrictions on their molecular weight, but liquid forms with an average molecular weight of about 200 to 600 are preferred for ease of addition.

[0050] The amount of surface protective agent added is preferably 0.01 parts by mass or more when the raw material alumina is 100 parts by mass, in order to allow the surface protective agent to exert its full effect. However, if the amount of surface protective agent added is too large, the effect of the surface protective agent will saturate, so it is preferable to add 10 parts by mass or less. The amount of surface protective agent added is more preferably 0.05 to 8 parts by mass, and even more preferably 0.1 to 5 parts by mass.

[0051] (Flame melting) A flame melting method is preferred as a method for producing alumina particles having a desired particle size and roundness. The flame melting method is a method in which raw material alumina is sprayed into a flame, liquefied, and then cooled and solidified. The flame melting method allows for the production of alumina particles while maintaining the particle size of the raw material alumina. In the flame melting method, the temperature of the flame melting furnace is preferably 1000°C or higher. In the flame melting method, the raw material supply rate can be adjusted as appropriate, but it is preferably 50 kg / h or less, and more preferably 10 kg / h or less. By setting the rate to this range, the amount of thermal energy applied to the alumina particles can be controlled within a predetermined range, making it easier to obtain alumina particles that meet the aforementioned requirements.

[0052] After the flame melting described above, alumina particles can be collected and classified using a cyclone or bag filter to obtain alumina particles with the desired properties. [Examples]

[0053] The following describes in detail this embodiment with reference to examples implemented to clarify its effects. However, this embodiment is not limited in any way to the following examples.

[0054] [Preparation of alumina particles] The alumina particles used in the examples and comparative examples were prepared as follows. Furthermore, various physical properties of the alumina particles (D50, average roundness, uranium content, and thorium content) were measured using the method described above and summarized in Table 1.

[0055] (1) Alumina particles A0 As a raw material, high-purity metallic aluminum obtained by the method described in Japanese Patent Publication No. 2010-106329 was prepared. After obtaining aluminum hydroxide from metallic aluminum by the aluminum alkoxide method described in Japanese Patent Publication No. 2018-048060, the aluminum hydroxide was calcined to obtain an alumina raw material.

[0056] Using a jet mill (horizontal jet mill pulverizer PJM-280SP manufactured by Nippon Pneumatic Mfg. Co., Ltd.), the raw material alumina was processed under the conditions of a supply rate of 30 kg / h and a gauge pressure of 0.5 MPa at the air supply port during pulverization, yielding alumina raw material powder with an average particle size of approximately 2 μm for secondary particles. The obtained alumina raw material powder was fed into a flame melting furnace and melted to obtain spherical alumina particles. The ambient temperature inside the flame melting furnace was set to 1250°C and the raw material supply rate to 5 kg / h. The obtained alumina particles were recovered using a cyclone and classified by cyclone classification to remove particles larger than 5 μm, obtaining alumina particle A0 (D50 = 2.3 μm).

[0057] (2) Alumina particles B0 Alumina particles were prepared using the same procedure as for alumina particles A0, and then subjected to classification by cyclone classification to remove particles larger than 10 μm, thereby obtaining alumina particles B0 (D50 = 5.1 μm).

[0058] (3) DAW05 Alumina particles (D50=6μm) from Denka Co., Ltd.'s DAW05 were used.

[0059] (4) AA-1.5 Alumina particles (D50 = 1.5 μm) of AA-1.5 manufactured by Sumitomo Chemical Co., Ltd. were used.

[0060] [Preparation of sheet-like resin compositions] Using the alumina particles, epoxy resin, and additives listed in Table 1, a sheet-like resin composition having the solid content composition listed in Table 2 was prepared by following the procedure described below.

[0061] (1) Preparation of varnish Mesogenic epoxy resin (phenylcyclohexyl type epoxy resin) (ME) or NC-7000 (manufactured by Nippon Kayaku Co., Ltd., naphthol-cresol novolac type epoxy resin) was dissolved in a mixed solvent of methyl ethyl ketone and cyclopentanone (mass ratio 3:1) to prepare a 30% by mass mixed solution. Furthermore, 4,4-diaminodiphenylmethane (DDM) (manufactured by TCI) was added as a curing agent at a concentration of 4.14% by mass per 100% by mass of the mixed solution to prepare a varnish.

[0062] • Mesogenic epoxy resin (ME) This is a prepolymer obtained by reacting trans-4-{4-(2,3-epoxypropoxy)phenyl}cyclohexyl=4-(2,3-epoxypropoxy)benzoate (an epoxy resin represented by the structural formula shown below) with 6-hydroxy-2-naphthoic acid.

[0063] [ka]

[0064] (2) Preparation of alumina / varnish mixture Alumina particles were added to the obtained varnish in the proportions shown in Table 2, and the mixture was kneaded at 2000 rpm for 60 seconds using a rotary-orbit mixer (manufactured by Sinky Co., Ltd.) to prepare an alumina / varnish mixture.

[0065] (3) Film formation and drying The obtained alumina / varnish mixture was applied to a PET substrate, and a film was formed using an applicator to achieve a post-curing thickness of 100-2000 μm. The film was then heated at 65°C for 5 minutes and then at 100°C for 15 minutes to evaporate the solvent and obtain a sheet-like resin composition (uncured). The thickness of the sheet-like resin composition (uncured) was as shown in Table 3. The solvent content of the obtained sheet-like resin composition was 0.1-3% by mass in all cases.

[0066] The amount of solvent in the sheet-like resin composition was determined by the following measurement. A 4 cm square sample was cut from each example and comparative example sheet-like resin composition, along with the PET substrate, and the mass W1 (g) of the sample (with PET substrate) was measured. Next, the sample was heated at 150°C for 10 minutes using a fully exhausted oven to evaporate all the solvent contained in the sample. After that, it was left at room temperature for 5 minutes to return to room temperature, and the mass W2 (g) of the heated sample (with PET substrate) was measured. The PET substrate was peeled off the heated sample, and the mass W3 (g) of the PET substrate was measured. The masses of the sample before and after heating were determined by subtracting W3 (g) from W1 (g) and W2 (g), respectively. The value obtained by subtracting the mass of the sample after heating (W2-W3) from the mass of the sample before heating (W1-W3) was taken as the mass of the solvent contained in the sheet-like resin composition. The ratio of the mass of the solvent to the mass of the sample before heating was taken as the solvent content (solvent amount). The formula for calculating the solvent content (solvent amount) is as shown in equation (1) below. Solvent volume (mass%) = {(W1-W3)-(W2-W3)} / (W2-W3) × 100···(1)

[0067] (4) Heat curing A sheet-like resin composition (uncured) was placed on a 12-inch silicon wafer and vacuum-press-molded at a pressure of 5 MPa and 140°C for 15 minutes using a press molding machine. The resulting material was then heated at atmospheric pressure and 175°C for 120 minutes to allow it to heat-cur. This yielded a cured sheet-like resin composition.

[0068] The following evaluations were performed on the cured sheet-like resin composition obtained. (1) Evaluation of surface condition and sealing properties The color of cured sheet-like resin compositions on silicon wafers was visually observed at an illuminance of 1000 lx. The observation results were evaluated based on the following criteria and summarized in Table 3. The unevenness in evaluations A to C was evaluated based on the area ratio of the white region (where the dispersibility of alumina particles is low, and voids between particles and resin, or particle aggregation, are observed) within the total area of ​​the sheet-like resin composition. However, even if there is uneven coloring, if there is no problem with sealing performance, the effect of the embodiment of the present invention (good sealing performance) is satisfied, and the result is judged as "acceptable". [Evaluation Criteria] A: Good sealing properties, and the area percentage of white, unevenly colored areas is less than 10%. B: Good sealing properties, and the area percentage of white, unevenly colored areas is 10% or more but less than 20%. C: Good sealing properties, and the area percentage of white, unevenly distributed areas is 50% or more. D: There are areas on the silicon wafer that are not covered with the resin composition, and irregularities occur on the surface of the resin composition. E: The resin composition is not sufficiently cured, resulting in insufficient sealing properties, and the area percentage of white, unevenly colored areas is 50% or more.

[0069] (2) Evaluation of alpha dose The alpha dose of a sheet-like resin composition was measured. The alpha dose was measured using a Model 1950 measuring device (Alpha Sciens). The measurement area of ​​the sample was 1000 cm². 2 The measurement time was set to 99 hours, and PR-10 gas (Ar 90%, CH 410%) was used as the counting gas. The measurement results were evaluated based on the following evaluation criteria and summarized in Table 3. [Evaluation Criteria] A: 0.002 cph / cm 2 below B: 0.002 cph / cm 2 Super 0.010cph / cm 2 below C: 0.010 cph / cm 2 Super 0.050cph / cm 2 below

[0070] (3) Evaluation of thermal conductivity The thermal conductivity of the cured sheet-like resin composition was measured. For the measurement of thermal conductivity, a 10 mm square section of the cured sheet-like resin composition was used. The thermal conductivity in the thickness direction of this test piece was measured using thermal wave thermal analysis with an ai-Phase Mobile (ai-Phase Mobile M3 type1, manufactured by ai-Phase Corporation). The measurement was performed under atmospheric conditions at 25°C. The measurement results were evaluated based on the following evaluation criteria and summarized in Table 3. [Evaluation Criteria] A:2.0W / (m·K) or more B: 0.27 W / (m·K) or more, less than 2.0 W / (m·K) C: Less than 0.27 W / (m·K)

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

[0074] Examples 1 to 11, which satisfy the conditions of the embodiments of the present invention, received surface condition and sealing performance evaluations of A to C, confirming that they are suitable as sheet-like resin compositions for forming sealing members. On the other hand, Comparative Example 1, which had a thinner sheet-like resin composition, exhibited poor sealing properties. Comparative Example 2, which had a thicker sheet-like resin composition, did not fully cure under the curing conditions (curing temperature and curing time) described above due to the thicker sheet thickness.

[0075] Furthermore, comparing Example 2 and Example 9, the D50 of the alumina particles was smaller for the alumina particles used in Example 9 than for the alumina particles used in Example 2, but the average roundness was lower for the alumina particles used in Example 9 than for the alumina particles used in Example 2. In these examples, the effect of the average roundness of the alumina particles on the sealing performance was more significant than the effect of the D50 of the alumina particles, which is why the sheet-like resin composition of Example 2 had better sealing performance than the sheet-like resin composition of Example 9.

Claims

1. It contains alumina particles and epoxy resin. The alumina particles have a particle diameter D50 of 10 μm or less at the cumulative 50% from the finest particle side of the volume-based cumulative particle size distribution. The thickness is 0.13 mm or more and 1.00 mm or less. Alpha dose: 0.05 cph / cm² ２ The following is a sheet-like resin composition.

2. The sheet-like resin composition according to claim 1, wherein the D50 of the alumina particles is less than 6.0 μm.

3. The sheet-like resin composition according to claim 1, wherein the thickness is 0.90 mm or less.

4. The sheet-like resin composition according to claim 1, wherein the average roundness of the alumina particles is 0.85 or higher.

5. The sheet-like resin composition according to claim 1, further comprising a solvent.

6. The sheet-like resin composition according to claim 5, wherein the ratio of the mass of alumina particles to the solid content of the sheet-like resin composition is 95% by mass or less.

7. The sheet-like resin composition according to claim 5, wherein the ratio of the mass of alumina particles to the solid content of the sheet-like resin composition is 50% by mass or more.

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