Resin composition and sheet molding compound, and alumina particles used in resin composition

Abstract

To provide a resin composition that contains alumina particles and a resin and is capable of reducing the alpha dose as compared with conventional methods. Provided is a resin composition containing alumina particles and a resin, wherein the alumina particles have a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio (L2 / L1) of the total length L2 of the internal grain boundaries to the length L1 of the outer edge of less than 139.1%.

Description

Resin composition and sheet molding compound, and alumina particles used in the resin composition

[0001] The present disclosure relates to resin compositions and sheet molding compounds, as well as alumina particles used in the resin compositions.

[0002] Heat generated by passing electricity through electronic components is likely to adversely affect the performance of the electronic components, so it is desirable for the heat to be dissipated quickly. Therefore, for example, it is desirable for the material constituting a semiconductor encapsulation member surrounding an IC chip to exhibit high thermal conductivity for heat dissipation. Thermally conductive members for heat dissipation generally use composites containing a thermally conductive filler and a resin, and alumina particles, which exhibit thermal conductivity, are used as the thermally conductive filler. Semiconductor devices are susceptible to the effects of alpha rays, and malfunctions (soft errors) caused by alpha rays are a problem. To solve this problem, it is important to use a resin composition for the encapsulation member that suppresses the amount of alpha rays emitted. To obtain a resin composition with a low alpha radiation dose, it is known to use alumina particles with an extremely small amount of uranium and thorium content (e.g., Patent Documents 1 to 3).

[0003] JP 2015-145336 A JP 2017-110146 A International Publication No. 2022 / 105697

[0004] In recent years, with the miniaturization of semiconductor devices and the narrowing of wiring pitches, semiconductor devices have become more susceptible to the effects of alpha rays. Therefore, resin compositions used in semiconductor encapsulation members are required to reduce the amount of alpha rays more than ever before. Patent Documents 1 to 3 disclose the control of the uranium and thorium contents contained in alumina particles, but do not consider further reduction of the amount of alpha rays.

[0005] In view of these circumstances, one embodiment of the present invention aims to provide a resin composition containing alumina particles and a resin, which can reduce the amount of alpha rays emitted compared to conventional resin compositions. Another embodiment of the present invention aims to provide a sheet-shaped composition (sheet molding compound) made of such a resin composition. Yet another embodiment of the present invention aims to provide alumina particles used in the resin composition.

[0006] A first aspect of the present invention is a resin composition comprising: alumina particles having a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio (L2 / L1) of a total length L2 of internal grain boundaries to a length L1 of an outer edge of the particles of less than 139.1%; and a resin.

[0007] A second aspect of the present invention is the resin composition according to the first aspect, wherein the alumina particles have a particle diameter D100 of 30 μm or less at 100% cumulative particle size from the fine particle side of the cumulative particle size distribution on a volume basis.

[0008] A third aspect of the present invention is the resin composition according to the first or second aspect, wherein the resin composition has an elastic modulus of 2.0 GPa or more.

[0009] A fourth aspect of the present invention is the resin composition according to any one of the first to third aspects, wherein the resin comprises at least one selected from the group consisting of an epoxy resin and a thermoplastic polyimide resin.

[0010] A fifth aspect of the present invention is the resin composition according to the fourth aspect, wherein the epoxy resin comprises at least one selected from the group consisting of mesogenic epoxy resins, phenylcyclohexyl epoxy resins, naphthalene epoxy resins, phenolic epoxy resins, biphenyl epoxy resins, butadiene epoxy resins, and bisphenol A epoxy resins.

[0011] A sixth aspect of the present invention is a sheet molding compound comprising the resin composition according to any one of the first to fifth aspects and having a thickness of 1000 μm or less.

[0012] A seventh aspect of the present invention is an alumina particle having a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio (L2 / L1) of a total length L2 of internal grain boundaries to an outer edge length L1 of less than 139.1%.

[0013] According to one embodiment of the present invention, a resin composition capable of reducing the amount of alpha rays emitted compared to conventional resin compositions can be provided. According to another embodiment of the present invention, a sheet molding compound comprising such a resin composition can be provided. According to yet another embodiment of the present invention, alumina particles for use in the resin composition can be provided.

[0014] The inventors have conducted extensive research to reduce the amount of alpha rays emitted from a resin composition, and as a result have found for the first time that the amount of alpha rays emitted from a resin composition can be effectively reduced by controlling the uranium (U) content and thorium (Th) content of the alumina particles used in the resin composition to extremely small amounts and reducing the content of grain boundaries in the alumina particles.

[0015] The mechanism by which grain boundaries in alumina particles affect the amount of α-rays emitted from a resin composition is not clear, but is speculated as follows. Alpha rays generated from U and Th in the alumina particles can be shielded by the alumina that constitutes the alumina particles. Here, it is speculated that the grain boundaries within the alumina particles are regions that have a low shielding effect against α-rays. Therefore, if the content of grain boundaries in alumina particles is high, the amount of α-rays emitted from the alumina particles increases, and the amount of α-rays emitted from a resin composition using such particles also increases. Therefore, it is thought that by limiting the content of grain boundaries in alumina particles, the amount of α-rays emitted from the alumina particles can be reduced, and as a result, a resin composition with a low amount of α-rays can be obtained.

[0016] The resin composition according to the embodiment, the alumina particles used in the resin composition, and the sheet molding compound (SMC) made of the resin composition will be described below.

[0017] [Resin Composition] The resin composition according to this embodiment contains alumina particles and a resin. The alumina particles used have a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio (L2 / L1) of the total length L2 of the grain boundaries within the alumina particles to the outer edge length L1 of the alumina particles of less than 139.1%. In this specification, the term "resin composition" is intended to include resin compositions in all states, including a liquid state before the resin in the resin composition is cured, a semi-cured state (B stage) in which the resin is semi-cured, and a cured state (C stage) in which the resin is fully cured. Here, "liquid state" also includes compositions in which the resin composition has fluidity, such as resin compositions containing solvents, as described below. "Semi-cured" refers to a state in which the resin composition has cured to the extent that it can be handled as a solid, but is not fully cured, and therefore the surface of the resin composition remains tacky. "Cured state" refers to a state in which the resin composition can be handled as a solid and has almost no tackiness on its surface.

[0018] The resin composition preferably has a modulus of elasticity (tensile modulus) of 2.0 GPa or more. The modulus of elasticity of the resin composition is more preferably 3.0 GPa or more, even more preferably 4.0 GPa or more, even more preferably 5.0 GPa or more, particularly preferably 6.0 GPa or more, and most preferably 7.0 GPa or more. The modulus of elasticity of the resin composition is usually 25.0 GPa or less, and may be 20.0 GPa or less. The modulus of elasticity is measured in a semi-cured or cured state. In particular, the modulus of elasticity of the cured resin composition is preferably 2.0 GPa or more, and a sealing member that can withstand deformation under general use conditions can be formed. The modulus of elasticity of the resin composition can be calculated from a stress-strain curve obtained in a tensile test in accordance with JIS K7161 (2014).

[0019] The rupture stress of the resin composition is preferably greater than 41.2 MPa, more preferably greater than 50.0 MPa, even more preferably greater than 60.0 MPa, and particularly preferably greater than 65.0 MPa. The rupture stress of the resin composition is measured in a semi-cured or cured state. It is particularly preferable that the rupture stress of the cured resin composition be greater than 41.2 MPa, greater than 50.0 MPa, greater than 60.0 MPa, or greater than 65.0 MPa, in this order. This improves the strength of the resulting sealing member and also improves dimensional stability against external energy such as heat. The rupture stress of the resin composition can be calculated from a stress-strain curve obtained in a tensile test in accordance with JIS K7161 (2014). The rupture stress of the semi-cured and cured resin compositions can be increased by adjusting the alumina particle content and curing conditions. Typically, the rupture stress of a cured resin composition is higher than that of a semi-cured resin composition.

[0020] Since alumina particles can reduce dielectric loss without impairing the flexibility inherent to resins, their blending ratios, relative to the total resin composition, are preferably 5 to 75 volume% resin, 95 to 25 volume% alumina particles, or 8 to 50 volume% resin, 92 to 50 volume% alumina particles, or 10 to 40 volume% resin, 90 to 60 volume% alumina particles, or 12 to 40 volume% resin, and 88 to 60 volume% alumina particles. Furthermore, in semi-cured and cured resin compositions, the total proportion of resin and alumina particles relative to the total resin composition is preferably 60 volume% or more, more preferably 70 volume% or more, and even more preferably 80 volume% or more. Furthermore, in semi-cured and cured resin compositions, the solids content relative to the total resin composition is preferably 80 volume% or more, more preferably 90 volume% or more, and even more preferably 95 volume% or more. The solid content of a resin composition refers to what remains as a solid when the resin composition is heated, excluding components that volatilize upon heating, such as the solvent. On the other hand, even if a component is liquid at 25°C, if it is incorporated into the solid content of the resin composition when heated, it is included in the solid content. The proportion of solids can be determined, for example, by determining the amount of solvent in the resin composition and subtracting it from the total. The amount of solvent in a resin composition can be measured, for example, by the following method. After measuring the mass W1 (g) of the resin composition, a sample is heated at 150°C for 10 minutes using a full exhaust oven to evaporate all of the solvent contained in the sample, and then the sample is left at room temperature for 5 minutes to return to room temperature, and the mass W2 (g) of the heated sample is measured. The amount of solvent in the resin composition can be determined by subtracting W2 (g) from W1 (g).

[0021] Next, the alumina particles and resin that constitute the resin composition will be described in detail.

[0022] [Alumina Particles] The alumina particles according to this embodiment have the following characteristics. The alumina particles preferably contain α-alumina particles. α-alumina is expected to have the effect of reducing the amount of α-rays emitted from the alumina particles, and the presence of α-alumina particles in the alumina particles can result in an improved effect of suppressing the amount of α-rays emitted from the resin composition. Furthermore, the α-alumina particles are also expected to have the effect of reducing the dielectric loss of the resin composition.

[0023] (Uranium Content and Thorium Content) The alumina particles have a uranium content of less than 550 ppb and a thorium content of less than 10 ppb. By suppressing the uranium content and thorium content of the alumina particles to extremely small amounts as described above, the amount of α-rays emitted from the alumina particles can be reduced, and as a result, the amount of α-rays emitted from the resin composition can be suppressed. This makes it possible to suppress malfunction of the semiconductor device due to α-rays when used as an encapsulating material for a semiconductor device.

[0024] The uranium content is preferably 300 ppb or less, more preferably 100 ppb or less, even more preferably 50 ppb or less, and particularly preferably 30 ppb or less, for example 10 ppb or less, or 5 ppb or less. The lower limit of the uranium content is not particularly limited, but 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 may be 0.1 ppb or more. The uranium content and thorium content can be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0025] (Ratio of the total length L2 of grain boundaries inside an alumina particle to the length L1 of the outer edge of the particle) Reducing the content of grain boundaries inside an alumina particle can improve the shielding effect against alpha rays generated from uranium and thorium inside the alumina particle, thereby reducing the amount of alpha rays emitted from the alumina particle. In this embodiment, the ratio (L2 / L1) of the total length L2 of the grain boundaries to the length L1 of the outer edge is introduced as an index of the content of grain boundaries inside an alumina particle. L1 and L2 are determined by observing the cross section of the alumina particle.

[0026] When the length of the outer edge of one alumina particle is L1 and the total length of the grain boundaries of that alumina particle is L2, alumina particles with a small L2 / L1 value have a low grain boundary content and emit a low amount of alpha rays. In particular, by making (L2 / L1) (%) less than 139.1%, the amount of emitted alpha rays can be further reduced when used as a filler for a resin composition. By reducing the amount of alpha rays emitted from the alumina particles, the amount of alpha rays emitted from a resin composition containing the alumina particles can also be reduced.

[0027] (L2 / L1) is preferably 120.0% or less, more preferably 100.0% or less, even more preferably 80.0% or less, even more preferably 60.0% or less, particularly preferably 52.0% or less, and most preferably 50.0% or less. The lower limit of (L2 / L1) is not particularly limited, but may be 10.0% or more, for example, 20.0% or more, 30.0% or more, 40.0% or more, or 43.0% or more. When the lower limit of L2 / L1 is within the above range, particle-resin interactions are more likely to occur, and in particular, the mechanical strength, such as the breaking stress, of the resin composition after semi-curing and curing is more likely to be increased. In order to control this L2 / L1 within a suitable range, single-crystal raw material particles may be used.

[0028] Furthermore, the fewer grain boundaries and cavities there are inside the alumina particles, the lower the dielectric loss of the alumina particles. Therefore, by controlling (L2 / L1) to less than 139.1%, a resin composition with low dielectric loss can be obtained.

[0029] The "total length L2 of the grain boundaries" refers to the sum of the grain boundaries contained within the alumina particle and does not include the outer edges of the alumina particle. The total length L2 of the grain boundaries is the sum of the total length L3 of the grain boundaries within the alumina particle and the total length L4 of the inner walls of the cavities (if any) within the alumina particle (i.e., L2 = L3 + L4).

[0030] (Particle diameter of alumina particles) The alumina particles preferably have a particle diameter D100 of 30 μm or less, which is the cumulative 100% particle diameter from the fine particle side of the volume-based cumulative particle size distribution. By using such alumina particles, a resin composition with lower dielectric loss can be obtained. D100 is preferably 30 μm or less, more preferably less than 20 μm, and particularly preferably 10 μm or less. The lower limit of D100 is not particularly limited, but may be 0.1 μm or more. Furthermore, the alumina particles preferably have a particle diameter D50 of 20 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less, and particularly preferably 3 μm or less, which is the cumulative 50% particle diameter from the fine particle side of the volume-based cumulative particle size distribution.

[0031] In one embodiment of the present invention, the alumina particles preferably have a ratio D90 / D50 of 5.0 or less, where D90 is the particle diameter at 90% of the cumulative particle size from the finest particle side of the cumulative particle size distribution (hereinafter sometimes simply referred to as "D90") and D50 is the particle diameter at 50% of the cumulative particle size from the finest particle side of the cumulative particle size distribution (hereinafter sometimes simply referred to as "D50"). This results in a sharp particle size distribution, facilitates appropriate particle-resin interaction, and particularly facilitates increasing the mechanical strength, such as the breaking stress, of the resin composition after semi-curing and curing. For example, D90 / D50 is more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 1.5 or less.

[0032] On the other hand, if the particle size distribution of the alumina particles is broad to some extent, the filling ability is improved by allowing small particles to fill the gaps between large particles, and more alumina particles can be kneaded into the resin, thereby improving the dimensional stability and breaking stress against external energy such as heat. Therefore, D90 / D50 is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more.

[0033] The particle diameters D100, D90, and D50 of the alumina particles can be determined by measuring the particle size distribution of the alumina particles by laser diffraction using, for example, a Microtrac MT3300EXII laser particle size distribution analyzer manufactured by Microtrac Bell Co., Ltd. D100 being 30 μm or less means that the particle diameter of all alumina particles is 30 μm or less, and that alumina particles having a particle diameter of more than 30 μm are substantially not contained. The particle diameter of the alumina particles in the resin composition can be measured by removing the resin contained in the resin composition, for example, by dissolving it in an organic solvent or by heating it to a temperature of 500 ° C. or higher to pyrolyze the resin, and then isolating only the alumina particles, and using the alumina particles.

[0034] Another method for determining the D100, D90, and D50 of alumina particles is to use image analysis. The resin composition may be subjected to cross-sectional observation using an SEM, and all alumina particles contained in a predetermined observation area (e.g., 200 μm × 200 μm) may be subjected to image analysis to measure their particle diameters (circle-equivalent diameters), and the particle diameters equivalent to D100, D90, and D50 may be calculated based on the measurement results.

[0035] [Method for Producing Alumina Particles] The alumina particles according to this embodiment can be produced, for example, by the method described below.

[0036] (Raw Alumina) Raw alumina is produced by a known method, such as the Bayer method, the ammonium alum method, the ammonium aluminum carbonate hydroxide method (AACH method), the solvent extraction method, the organoaluminum hydrolysis method (aluminum alkoxide method), or a melt growth method such as the CZ method, the Verneuil method, the chiroporous method, the Bridgman method, or the EFG method.

[0037] In the case of the Bayer process, raw alumina can be produced by calcining aluminum hydroxide obtained from bauxite. Furthermore, the ammonium alum process, the AACH process, the solvent extraction process, and the aluminum alkoxide process are preferred because they allow for the production of high-purity raw alumina with low uranium and thorium contents. Raw alumina produced by these processes, with a uranium content of less than 550 ppb and a thorium content of less than 10 ppb, respectively, is preferably used to produce alumina particles, since alumina particles with reduced uranium and thorium contents can be obtained.

[0038] (Pulverization of Raw Alumina) In order to easily obtain alumina particles of a desired size by flame melting, the raw alumina is pulverized to obtain an alumina raw powder to be subjected to flame melting. Pulverization of the raw alumina can be carried out by a known method such as a vibration mill, a bead mill, a ball mill, or a jet mill, and may be carried out in either a dry or wet state.

[0039] A surface protective agent may be used in the above-described pulverization. The surface protective agent not only protects the surface of the alumina raw material powder after pulverization but may also have the function of inactivating the surface of the alumina raw material powder. The surface inactivation function of the surface protective agent can reduce aggregation of the alumina raw material powder. Therefore, the surface protective agent is suitable for obtaining alumina particles of a desired particle size after flame fusion using raw alumina with a high BET specific surface area, which is prone to aggregation. Suitable surface protective agents 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 protective agents may be used alone, or two or more may be used in combination. Among these, glycols are preferred, and one or more of ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol are particularly preferred.

[0040] The molecular weight of the polyethylene glycol and polypropylene glycol preferably used as the surface protective agent is not particularly limited, but liquids with an average molecular weight of about 200 to 600 are preferred for ease of addition.

[0041] The amount of the surface protective agent added is preferably 0.01 parts by mass or more relative to 100 parts by mass of raw alumina in order to fully exert the effect of the surface protective agent, and is preferably 10 parts by mass or less because the effect of the surface protective agent becomes saturated if the amount of the surface protective agent added is too large. The amount of the 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.

[0042] (Flame fusion) The flame fusion method is a method in which raw alumina is sprayed into a flame, turned into droplets, and then cooled and solidified. According to the flame fusion method, alumina particles can be obtained while roughly maintaining the particle diameter of the raw alumina. In the flame fusion method, the temperature of the flame fusion furnace is preferably 1000°C or higher. In the flame fusion method, the raw material supply rate can be adjusted as appropriate, but by setting it to preferably 50 kg / h or less, more preferably 10 kg / h or less, 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 above-mentioned predetermined requirements.

[0043] After the flame fusion, the alumina particles are collected using a cyclone or a bag filter and classified to obtain alumina particles having the desired properties.

[0044] [Resin] The resin used in the resin composition preferably includes one or more resins selected from the group consisting of epoxy resins and thermoplastic polyimides, and more preferably includes an epoxy resin. Preferred epoxy resins include mesogenic epoxy resins, phenylcyclohexyl epoxy resins, naphthalene epoxy resins, phenolic epoxy resins, biphenyl epoxy resins, butadiene epoxy resins, and bisphenol A epoxy resins. The mesogenic epoxy resin is an epoxy resin having a mesogenic group, and is preferably a resin that exhibits a phase transition temperature in the temperature range of 100°C to 200°C and exhibits liquid crystallinity. The resin contained in the resin composition may include one or more epoxy resins. That is, the resin contained in the resin composition may include one or more epoxy resins selected from the group consisting of mesogenic epoxy resins, phenylcyclohexyl epoxy resins, naphthalene epoxy resins, phenolic epoxy resins, biphenyl epoxy resins, butadiene epoxy resins, and bisphenol A epoxy resins, and may further include a thermoplastic polyimide. These resins are expected to have the effect of blocking alpha rays emitted from alumina particles, and because they have low dielectric loss, it is possible to obtain a resin composition with even lower alpha rays and even lower dielectric loss.

[0045] Furthermore, these resin compositions may contain 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, either singly or in combination, as long as the effects of the invention are not impaired. In one embodiment of the present application, the resin composition (particularly a liquid or semi-cured resin composition) may contain a solvent. When the resin composition contains a solvent, it is highly fluid, can be easily deformed to fit the fine structures of IC chips and substrates, and can seal dense structures without gaps. Known solvents may be used, and are not limited as long as they can dissolve the resin. Examples of such solvents 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, and nitrile-based solvents. Ketone-based solvents and ester-based solvents are preferred because they are good solvents for epoxy resins and provide excellent coatability for the resulting resin composition.

[0046] In a preferred embodiment of the present invention, the resin composition comprises alumina particles, an epoxy resin, a solvent, and a curing agent, such as an amine-based curing agent such as 4,4-diaminodiphenylmethane.

[0047] [Method for Producing Resin Composition] The method for producing the resin composition will be described. A resin composition can be obtained by mixing the alumina particles according to this embodiment with a resin using a commonly used known method. For example, when the resin is liquid (e.g., liquid epoxy resin), the liquid resin, alumina particles, and a curing agent are mixed, and then cured with heat or ultraviolet light to obtain a resin composition. Known curing agents, mixing methods, and curing methods can be used. On the other hand, when the resin is solid (e.g., epoxy resin, polyolefin resin, acrylic resin, etc.), the alumina particles and resin can be mixed, and then kneaded using a known method such as melt kneading, or the resin, alumina particles, and curing agent can be dissolved and mixed in a solvent to obtain the desired resin composition. The resin composition may contain a solvent.

[0048] The resin composition according to this embodiment includes resin compositions in all states, including a liquid state before the resin in the resin composition is cured, a semi-cured state (B stage) in which the resin is semi-cured, and a cured state (C stage) in which the resin is completely cured. Liquid resin compositions include blends in which alumina powder and resin are blended in a predetermined ratio, mixtures obtained by mixing such blends, and molded articles obtained by molding such mixtures. Semi-cured resin compositions include resin compositions obtained by semi-curing the resin contained in the mixture or molded article. Cured resin compositions include resin compositions obtained by completely curing the resin contained in the mixture, molded article, or semi-cured article.

[0049] [Sheet Molding Compound (SMC)] A sheet molding compound (SMC) can be provided using the resin composition according to the embodiment. The SMC is a resin composition molded into a sheet. The SMC preferably has fluidity when heated and pressurized, and may be in a semi-cured state. The SMC preferably has a thickness of 1000 μm or less. When incorporated into a semiconductor device, the semiconductor device can be made smaller and lighter, and the sealing performance can be improved when sealing an IC chip. The thickness is more preferably 800 μm or less, even more preferably 600 μm, even more preferably 500 μm or less, particularly preferably 400 μm or less, and particularly preferably 300 μm or less. The lower limit of the thickness is not particularly limited, but may be, for example, 10 μm or more, 50 μm or more, or even 100 μm or more, or 150 μm or more, depending on the dimensions of commonly used SMCs and the ability to enhance the sealing performance of IC chips.

[0050] SMCs can be produced by known methods. For example, an uncured resin composition is applied to a substrate, a protective film is placed thereon, and the resin composition is semi-cured. Another example is a solvent-containing uncured resin composition applied to a substrate, the solvent is removed from the resin composition by drying, or the like, and then a protective film is placed thereon. When using an SMC, the protective film is peeled off, the SMC is pressure-bonded to a wafer or the like, the substrate is removed, and the SMC is post-cured.

[0051] The resin composition and SMC of the present invention have a low alpha radiation dose and low dielectric loss, and are therefore suitable as sealing materials for semiconductor elements.

[0052] [Preparation of Alumina Particles] The alumina particles (A to E) used in the resin compositions of Samples No. 1 to 8 were prepared as follows.

[0053] (Alumina particles A and B used in samples Nos. 1 to 5) As alumina particles, the following alumina particles A (used in samples Nos. 3 to 5) and alumina particles B (used in samples Nos. 1 and 2) were prepared.

[0054] As the raw alumina, γ-alumina obtained by the ammonium alum method (the average particle size of the primary particles calculated from the value of the BET specific surface area described below was 13 nm) was used. The BET specific surface area of ​​this γ-alumina measured by the nitrogen adsorption method was 120 m ２ Before pulverization, 4 mass % of propylene glycol was added as a surface protective agent to the raw alumina and mixed.

[0055] Next, the mixture was treated using a jet mill pulverizer (horizontal jet mill pulverizer PJM-280SP manufactured by Nippon Pneumatic Mfg. Co., Ltd.) under the conditions of a raw material alumina feed rate of 30 kg / h and a gauge pressure at the air supply port during pulverization of 0.5 MPa, to obtain an alumina raw material powder having an average particle size of secondary particles of about 2 μm.

[0056] The obtained alumina raw material powder was charged into a flame fusion furnace and melted to obtain spherical alumina particles. The atmospheric temperature in the flame fusion furnace was set to 1250°C, and the raw material feed rate was set to 5 kg / h. The obtained alumina particles were recovered using a cyclone and classified by cyclone classification to remove particles of 20 μm or larger, thereby obtaining alumina particles A (D50 = 5.1 μm, used for Samples No. 3 to 5). Furthermore, particles of 10 μm or larger were removed to obtain alumina particles B (D50 = 2.3 μm, used for Samples No. 1 and 2).

[0057] (Alumina Particles C Used in Sample No. 6) Sample No. 6 used alumina particles C prepared by the following procedure. Alumina raw material particles made of single-crystal alumina having a D50 of 3.5 μm were prepared and charged into a flame melting furnace to melt and obtain spheroidized alumina particles. The obtained alumina particles were subjected to a classification process using a cyclone classifier to remove particles of 20 μm or larger, thereby obtaining alumina particles C.

[0058] (Alumina particles D used in sample No. 7) For sample No. 7, alumina particles (alumina particles D) manufactured by Denka DAW05 were used.

[0059] (Alumina Particles E Used in Sample No. 8) For Sample No. 8, alumina mixed particles (alumina particles E) prepared by mixing alumina particles B and AA-18 manufactured by Sumitomo Chemical Co., Ltd. in a mass ratio of 9:1 were used.

[0060] The alumina particles used in each sample were subjected to the following measurements.

[0061] [Particle size distribution of alumina particles] The particle size distribution of alumina particles was measured by laser diffraction using a Microtrac MT3300EXII laser particle size distribution analyzer manufactured by Microtrac Bell Co., Ltd. The D50, D90, and D100 were determined from the particle size distribution measurement results. The measurement sample was an alumina particle dispersion obtained by adding the alumina particles to be measured to a 0.2% by mass aqueous solution of sodium hexametaphosphate so that the laser scattering intensity was appropriate, and dispersing the alumina particles for 5 minutes using the built-in ultrasonic wave at 40 W. The refractive index of alumina was 1.76.

[0062] [Uranium and Thorium Contents of Alumina Particles] The uranium content (U content) and thorium content (Th content) contained in the alumina particles were measured as follows. First, the alumina particles were placed in a mixed aqueous solution of sulfuric acid and phosphoric acid, and heated to dissolve the alumina particles, preparing an aqueous solution. Then, the aqueous solution was contacted with a cyclohexane solution of tributyl phosphate, which is commonly used as an extractant for uranium, to extract the uranium contained in the aqueous solution. Then, the uranium was transferred to the aqueous phase by back-extraction, where it was contacted again with pure water, and the intensities of U 238 amu and Th 232 amu were measured using ICP-MS. A standard solution manufactured by SPEX was used to create a calibration curve.

[0063] [BET Specific Surface Area of ​​Alumina Particles] A Shimadzu Flowsorb III 2310 specific surface area measuring device was used, and the nitrogen adsorption BET specific surface area was determined by the single-point nitrogen adsorption method in accordance with the method specified in JIS-Z8830 (2013). The measurement conditions were as follows: Carrier gas: nitrogen / helium mixed gas; Sample amount: 0.1 g; Sample pretreatment conditions: 20 minutes at 200°C; Nitrogen adsorption temperature: liquid nitrogen temperature (-196°C or lower); Nitrogen desorption temperature: room temperature (approximately 20°C).

[0064] [Measurement of the length L1 of the outer edge of an alumina particle and the total length L2 of the grain boundary inside the particle] Samples for cross-sectional observation were prepared using alumina particles Nos. 1 to 6. To prepare the cross-sectional observation samples, the alumina particles were embedded in resin, and then the resin and alumina particles were cut using a diamond cutter. Subsequently, a protective film of platinum was vapor-deposited on the cross-section, and the cross-section was prepared by Ar ion milling. The sample was then fixed to the SEM sample stage with Cu double-sided tape, and SEM-EBSD measurement was performed without vapor deposition. The observation position was determined so that two or more alumina particles were completely contained within the observation area (i.e., two or more alumina particles did not come into contact with the frame of the observation area). All of the measured alumina particles were α-alumina particles.

[0065] The following equipment was used for sample pretreatment and EBSD measurement: Equipment used Ion milling equipment: IM-4000 (manufactured by Hitachi, Ltd.) Ion sputtering equipment: E-1030 (manufactured by Hitachi, Ltd.) Ultra-high resolution field emission scanning electron microscope: JSM-7800F Prime (manufactured by JEOL Ltd.) Backscattered electron diffraction equipment: Digiview V (manufactured by TSL)

[0066] The conditions for the EBSD measurement were as follows: Measurement area: 500.0 μm×400.0 μm Acceleration voltage: 20.0 kV Magnification: ×500 Vacuum degree: 30 Pa

[0067] In the obtained EBSD image, two or more alumina particles that were not in contact with the frame of the observation area were selected, and the average of the outer edge lengths L1 of each alumina particle was calculated using image processing software Image J (manufactured by the National Institute of Health). The "total grain boundary length L2" was the sum of the grain boundaries contained inside the alumina particle, excluding the outer edges of the alumina particle. The total grain boundary length L2 was calculated by adding the total length of the grain boundaries inside the alumina particle and the total length of the inner walls of the cavities (if any) inside the alumina particle.

[0068] The ratio of the total length L2 of the grain boundaries to the length L1 of the outer edge (L2 / L1) was expressed as a percentage (%). The more grain boundaries and voids there are inside the alumina particle, the larger the value of L2 / L1 (%).

[0069] [α-ray dose emitted from alumina particles] The α-ray dose emitted from alumina particles was measured using a measuring device Model 1950 (manufactured by Alpha Sciences). The measurement area of ​​the sample was 1000 cm ２ The measurement time was 99 hours, and the counting gas was PR-10 gas (Ar 90%, CH ４ 10%) was used.

[0070] [Preparation of Resin Composition] Alumina particles, resin, etc. were kneaded to prepare resin compositions (Samples No. 1 to 8). The types of resin used are shown in Table 1, and the amounts of alumina particles added are shown in Table 3. The elastic modulus of the resin not containing alumina particles when cured was measured, and this is shown in the "Elastic Modulus" column of "Resin" in Table 3. Specifically, the resin compositions of Samples No. 1 to 8 were prepared according to the following preparation method. In Table 3, "Resin composition" refers to the resin composition in a cured state.

[0071] (Samples Nos. 1 to 4, 6 to 8) (1) Preparation of Varnish A 30% by mass mixed solution was prepared by dissolving the resin shown in Table 1 in the solvent shown in Table 1. Furthermore, 0.074% by mass of a curing agent (4,4-diaminodiphenylmethane (manufactured by TCI)) was added relative to 100% by mass of the mixed solution to prepare a varnish.

[0072] (2) Preparation of Alumina / Varnish Mixture Alumina particles were added to the obtained varnish, and the mixture was kneaded using a planetary centrifugal mixer (manufactured by Thinky Corporation) to prepare an alumina / varnish mixture.

[0073] (3) Film Formation The resulting alumina / varnish mixture was applied to a PET substrate and formed into a film using an applicator so that the film thickness after thermal curing would be 150 to 200 μm, thereby obtaining a resin composition before curing.

[0074] (4) Thermal Curing The obtained uncured resin composition was allowed to stand at room temperature for 1 hour, then heated at 140°C for 15 minutes, and then vacuum press molded at 140°C for 20 minutes at a pressure of 0.5 MPa using a press molding machine. The composition was then heated at 180°C for 120 minutes at normal pressure to thermally cure. This resulted in cured resin compositions (Samples Nos. 1 to 4 and 6 to 8). The resin compositions of Samples Nos. 1 to 4 and 6 to 8 had a solids content of 95% or more by volume relative to the total resin composition.

[0075] (Sample No. 5) (1) Preparation of Varnish The resins shown in Table 1 were dissolved in the solvents shown in Table 1 to prepare 12% by mass mixed solutions.

[0076] (2) Preparation of Alumina / Varnish Mixture Alumina particles were added to the obtained varnish and kneaded using a planetary centrifugal mixer (manufactured by Thinky Corporation) to prepare an alumina / varnish mixture.

[0077] (3) Film Formation The resulting alumina / varnish mixture was applied to a PET substrate and formed into a film using an applicator so that the film thickness after thermal curing would be 150 to 200 μm, thereby obtaining a resin composition before curing.

[0078] (4) Thermal Curing The obtained resin composition before curing was heated at 120°C for 3 hours, then heated from 25°C to 360°C in a nitrogen atmosphere, and heated at 360°C for 30 minutes to be thermally cured, thereby obtaining a cured resin composition (Sample No. 5).

[0079]

[0080] Details of the types of resins listed in Table 1 are as follows:

[0081] Mesogenic epoxy resin (A) 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 below) with 6-hydroxy-2-naphthoic acid.

[0082]

[0083] Mixture of JP-100 and HP6000 This mixture was prepared by mixing JP-100 (manufactured by Nippon Soda), an epoxidized polybutadiene, and HP-6000 (manufactured by DIC), a naphthalene-based epoxy resin, in a mass ratio of 1:9.

[0084] Thermoplastic polyimide (TPI) A compound synthesized under the following conditions was used for the thermoplastic polyimide. 9.87 g (46.5 mmol) of m-Tb and 122.35 g (418.5 mmol) of TPE-R were dissolved in 1,890 g of DMAc, and then 30.26 g (138.7 mmol) of PMDA and 95.25 g (323.7 mmol) of BPDA were added in that order, followed by stirring at 20°C for 3 hours under a nitrogen atmosphere. The molar ratio of diamine monomer to acid dianhydride monomer used was 1.01.

[0085] [Dielectric Loss of Resin Composition] The dielectric loss of the cured resin compositions (samples No. 1 to 8) was measured under the following conditions: Measuring device: Network analyzer 8720ES (Agilent Technologies) Test piece dimensions: 50 mm x 50 mm Measurement frequency: 12 GHz Test environment: 22°C / 59% RH

[0086] [α-ray Dose Emitted from Resin Composition] The α-ray dose emitted from the resin composition was measured using a measuring device Model 1950 (manufactured by Alpha Sciences). The measurement area of ​​the sample was 1000 cm ２ The measurement time was 99 hours, and the counting gas was PR-10 gas (Ar 90%, CH ４ 10%) was used.

[0087] [Elastic Modulus of Resin Composition] The elastic modulus of the resin composition was measured in accordance with JIS K7161 (2014). Specifically, a tensile test was performed on the cured resin composition under the following conditions, and the obtained stress-strain curve was analyzed and calculated. Testing equipment: Autograph AGS-X (manufactured by Shimadzu Corporation) Load cell: 1 kN Test piece dimensions: 100 mm x 10 mm Testing environment: 22°C / 59% RH Analysis software: TRAPEZIUMX

[0088] [Rupture Stress of Resin Composition] The rupture stress of the resin composition was calculated by analyzing the stress-strain curve obtained in the tensile test. The rupture stresses of the resin compositions of Samples 1 to 4 and 7 were 70.2 MPa, 78.4 MPa, 47.4 MPa, 63.8 MPa and 41.2 MPa, respectively.

[0089] The results of various measurements of the alumina particles are shown in Table 2, and the types of resins used (and their elastic moduli) and the results of various measurements of the resin compositions are shown in Table 3. In the table, "-" indicates that no measurement was performed.

[0090]

[0091]

[0092] The measurement results are discussed below. The resin compositions of Samples 1 to 4 and 6, which meet the requirements of the present embodiment, emitted low amounts of alpha rays. On the other hand, the resin composition of Sample 7, which does not meet the requirements of the present embodiment, emitted high amounts of alpha rays.

[0093] From the results of particle size distribution measurements, it was confirmed that alumina particles A to C used in the resin compositions of Samples No. 1 to 6 (Examples) contained no particles of 20 μm or larger (i.e., D100 was less than 20 μm), and that alumina particles B contained no particles of 10 μm or larger. On the other hand, it was confirmed that alumina particles D and E used in the resin compositions of Samples No. 7 to 8 (Comparative Examples) contained particles of 20 μm or larger (i.e., D100 was 20 μm or larger).

[0094] Samples Nos. 1 to 6 had low dielectric loss, and in particular, Samples Nos. 1, 3, and 6 had extremely low dielectric loss. On the other hand, Samples Nos. 7 and 8 had high dielectric loss.

Claims

1. A resin composition comprising: alumina particles having a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio (L2 / L1) of the total length L2 of the internal grain boundaries to the outer edge length L1 of less than 139.1%; and a resin.

2. The resin composition according to claim 1, wherein the alumina particles have a particle diameter D100 of 30 μm or less at 100% cumulative from the fine particle side of the volume-based cumulative particle size distribution.

3. The resin composition according to claim 1, having an elastic modulus of 2.0 GPa or more.

4. The resin composition according to claim 1, wherein the resin comprises at least one selected from the group consisting of epoxy resins and thermoplastic polyimide resins.

5. The resin composition according to claim 4, wherein the epoxy resin comprises at least one selected from the group consisting of mesogen-based epoxy resins, naphthalene-based epoxy resins, phenylcyclohexyl-based epoxy resins, phenol-based epoxy resins, biphenyl-based epoxy resins, butadiene-based epoxy resins, and bisphenol A-based epoxy resins.

6. A sheet molding compound comprising the resin composition according to any one of claims 1 to 5 and having a thickness of 1000 μm or less.

7. Alumina particles having a uranium content of less than 550 ppb, a thorium content of less than 10 ppb, and a ratio of the total length L2 of the internal grain boundaries to the length L1 of the outer edge (L2 / L1) of less than 139.1%.

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