Thermosetting resin composition and use thereof

Abstract

To provide a thermosetting resin composition which becomes a cured product having high heat resistance and excellent tracking resistance.SOLUTION: The thermosetting resin composition contains (A) an aliphatic bismaleimide compound represented by the following formula (1) (where A represents a C5-12 divalent aliphatic hydrocarbon group) and (B) an epoxy resin having two or more epoxy groups in one molecule. A content of the component (A) is 20 to 95 mass% based on the total of the component (A) and the component (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cured thermosetting resin suitable for use as an encapsulant for power semiconductors, and to uses thereof. [Background technology]

[0002] SiC power semiconductors have attracted considerable attention due to their potential for more efficient power utilization and device miniaturization compared to conventional Si power semiconductors. In particular, in recent years, devices have become even smaller and are capable of handling larger currents. Accordingly, there is a strong demand for the development of encapsulating materials with high heat resistance and excellent tracking resistance, as measured by the comparative tracking index (CTI).

[0003] First, regarding high heat resistance, Patent Documents 1 and 2 report that resin compositions containing maleimide resins both have a glass transition temperature (Tg) exceeding 300° C. and a 5% weight loss temperature (Td5) exceeding 400° C. This is presumably due to the high crosslink density that is characteristic of maleimide resins, in addition to the rigidity of both resins due to the aromatic ring components in their structures.

[0004] Next, with regard to tracking resistance, Patent Documents 3 and 4 report that excellent tracking resistance can be achieved by introducing an alicyclic structure into the epoxy resin structure. This is presumably due to the fact that reducing the proportion of aromatic rings in the structure suppresses the formation of carbonized conductive paths, which are the cause of tracking. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-193628 [Patent Document 2] Japanese Patent Application Publication No. 2019-064926 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-213299 [Patent Document 4] Japanese Patent Publication No. 2023-019588 Summary of the Invention [Problem to be solved by the invention]

[0006] However, resin compositions containing maleimide resins with high heat resistance have poor tracking resistance, and epoxy resin-containing resin compositions with tracking resistance have poor heat resistance. Therefore, an object of the present invention is to provide a thermosetting resin composition that gives a cured product having high heat resistance and excellent tracking resistance, and a semiconductor encapsulant produced using the thermosetting resin composition. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have found that the following thermosetting resin composition can achieve the above object, and have completed the present invention.

[0008] [1] (A) an aliphatic bismaleimide compound represented by the following formula (1): [ka] (In formula (1), A is a divalent aliphatic hydrocarbon group having 5 to 12 carbon atoms.) and (B) Epoxy resin having two or more epoxy groups in one molecule A thermosetting resin composition comprising: A thermosetting resin composition in which the component (A) accounts for 20 to 95 mass % of the total of the components (A) and (B). [2] The thermosetting resin composition according to [1], wherein in the formula (1), A is a divalent chain aliphatic hydrocarbon group having 5 to 12 carbon atoms. [3] The thermosetting resin composition according to [1] or [2], further comprising (C) a curing accelerator. [4] The thermosetting resin composition according to [3], wherein the component (C) comprises one or more selected from the group consisting of imidazole-based curing accelerators, organophosphorus-based curing accelerators, and tertiary amine-based curing accelerators. [5] A semiconductor encapsulant comprising the thermosetting resin composition according to any one of [1] to [4]. [6] [5] The semiconductor encapsulant according to [5], wherein the semiconductor is a power semiconductor. [Effects of the Invention]

[0009] The cured product of the thermosetting resin composition of the present invention has a high glass transition temperature (Tg), high heat resistance, and excellent tracking resistance. Therefore, the composition of the present invention is useful as an encapsulant for semiconductors, particularly for power semiconductors, which require high heat resistance and excellent tracking resistance. DETAILED DESCRIPTION OF THE INVENTION

[0010] [(A) Aliphatic bismaleimide compound] The component (A) used in the present invention is an aliphatic bismaleimide compound represented by the following formula (1). [ka] In the above formula (1), A is a divalent aliphatic hydrocarbon group having 5 to 12 carbon atoms, preferably 6 to 9. The aliphatic hydrocarbon group represented by A may be linear, branched, or cyclic. In particular, the aliphatic hydrocarbon group represented by A is preferably linear or branched.

[0011] The aliphatic bismaleimide compound of component (A) is not particularly limited in terms of its properties at room temperature (25°C ± 10°C) or number average molecular weight, but the number average molecular weight is preferably 200 to 10,000, more preferably 200 to 5,000, and even more preferably 200 to 1,000. In this specification, the number average molecular weight is a number average molecular weight calculated using polystyrene standards by gel permeation chromatography (GPC) measurement under the following measurement conditions. [GPC measurement conditions] Developing solvent: tetrahydrofuran (THF) Flow rate: 0.35mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperHZ4000(4.6mmI.D.×15cm×1) TSKgel SuperHZ3000(4.6mmI.D.×15cm×1) TSKgel SuperHZ2000 (4.6mmI.D.×15cm×2) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 5 μL (0.2% by mass THF solution)

[0012] Furthermore, if the group A in the aliphatic bismaleimide compound of component (A) has fewer than 5 carbon atoms, the melting point of component (A) alone will be around 200°C, which overlaps with the temperature range in which the curing reaction proceeds, making it difficult to obtain a uniform cured product. Therefore, from the perspective of moldability of the composition, the group A in the aliphatic bismaleimide compound of component (A) must have 5 or more carbon atoms. Furthermore, from the perspective of synthesis and availability of the diamine compound that serves as the raw material for component (A), the upper limit on the number of carbon atoms in group A is 12. Furthermore, the properties of the aliphatic bismaleimide compound of component (A) at room temperature are not particularly limited, as described above. The melting point of the aliphatic bismaleimide compound of component (A) is preferably less than 160°C, and more preferably less than 140°C.

[0013] The aliphatic bismaleimide compound of component (A) may be used alone or in combination of two or more. The composition of the present invention is characterized in that the proportion of component (A) relative to the total of components (A) and (B) (100% by mass) is 20 to 95% by mass, and preferably 50 to 95% by mass. When the quantitative ratio of components (A) to (B) is within this range, a crack-free cured product is easily obtained. In addition, the total amount of components (A) and (B) in the composition of the present invention is preferably 0.50 to 91 mass %, and more preferably 0.99 to 76 mass %.

[0014] [(B) Epoxy resin] The epoxy resin (B) is added for the purposes of accelerating the reaction of the aliphatic bismaleimide compound (A) and maintaining the shape of the cured product.

[0015] The epoxy resin has two or more epoxy groups in one molecule, and any conventionally known epoxy resin can be used. Examples of the epoxy resin include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, bisphenol A novolac-type epoxy resins, and bisphenol F novolac-type epoxy resins; alicyclic epoxy resins such as dicyclopentadiene-type epoxy resins and 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate; polyfunctional phenol-type epoxy resins such as resorcinol-type epoxy resins and resorcinol novolac-type epoxy resins; stilbene-type epoxy resins, triazine skeleton-containing epoxy resins, fluorene skeleton-containing epoxy resins, triphenolalkane-type epoxy resins, biphenyl-type epoxy resins, xylylene-type epoxy resins, biphenylaralkyl-type epoxy resins, naphthalene-type epoxy resins, and diglycidyl ether compounds of polycyclic aromatics such as anthracene, and phosphorus-containing epoxy resins obtained by introducing a phosphorus compound into any of these. Among these, epoxy resins having cyclic saturated hydrocarbon groups in the molecule are preferably used because they have superior tracking resistance. These may be used alone or in combination of two or more.

[0016] [(C) Curing accelerator] The curing accelerator of component (C) is an optional component that is blended to accelerate the curing properties of the aliphatic bismaleimide compound (A), and generally known curing accelerators such as imidazole-based curing accelerators, organophosphorus-based curing accelerators, and tertiary amine-based curing accelerators can be used. Examples of organic phosphorus curing accelerators include phosphines such as triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine; phosphine-borane complexes such as triphenylphosphine-triphenylborane; phosphonium borate salts such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tri-tert-butylphosphonium tetraphenylborate; and bis(tetrabutylphosphonium) dihydrogenpyromellitate. Examples of the tertiary amine curing accelerator include tertiary amine compounds such as triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo[5.4.0]undecene-7; and salts of tertiary amine compounds such as 1,8-diazabicyclo[5.4.0]undecene-7. Examples of the imidazole curing accelerator include 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole. The component (C) may be used alone or in combination of two or more.

[0017] In order to promote curing, the amount of (C) curing accelerator to be added is preferably 0.01 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the total of the (A) and (B) components.

[0018] [Other additives] In addition to the components (A) to (C), other additives may be added to the thermosetting resin composition of the present invention as needed, provided that the objects and effects of the present invention are not impaired. Examples of such additives include inorganic fillers, flame retardants, ion trapping agents, antioxidants, adhesion promoters, stress reducing agents, and colorants.

[0019] Inorganic fillers are blended into thermosetting resin compositions to improve their resin strength and reduce their thermal expansion. Examples of inorganic fillers include silicas (e.g., fused silica, crystalline silica, cristobalite, etc.), alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, glass fiber, magnesium oxide, etc. The average particle size and shape of these inorganic fillers can be selected depending on the application.

[0020] In order to strengthen the bond between the resin and the inorganic filler, it is preferable to use an inorganic filler that has been surface-treated in advance with a coupling agent such as a silane coupling agent or a titanate coupling agent. Examples of such coupling agents include epoxy silanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino silanes such as N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, the reaction product of imidazole and γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and mercaptosilanes such as γ-mercaptosilane and γ-episulfidoxypropyltrimethoxysilane. The amount of coupling agent used in the surface treatment and the surface treatment method are not particularly limited.

[0021] The amount of inorganic filler added is preferably 10 to 20,000 parts by mass, and more preferably 30 to 10,000 parts by mass, per 100 parts by mass of the total of the components (A) and (B).

[0022] The flame retardant is added for the purpose of imparting flame retardancy. The flame retardant is not particularly limited, and any known flame retardant can be used, such as a phosphazene compound, a silicone compound, zinc molybdate-supported talc, zinc molybdate-supported zinc oxide, aluminum hydroxide, magnesium hydroxide, or molybdenum oxide.

[0023] The ion trapping agent is added for the purpose of trapping ionic impurities contained in the resin composition and preventing thermal degradation and moisture absorption degradation. The ion trapping agent is not particularly limited and any known agent can be used, such as hydrotalcites, bismuth hydroxide compounds, and rare earth oxides.

[0024] The antioxidant is not particularly limited, and examples thereof include n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)acetate, neododecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, dodecyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, ethyl Octadecyl-α-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, Octadecyl-α-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, Octadecyl-α-(4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(n-octylthio)ethyl-3,5-di-t-butyl-4-hydroxyphenylacetate, 2-(n-octadecylthio)ethyl-3, 5-Di-t-butyl-4-hydroxyphenyl acetate, 2-(n-octadecylthio)ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(2-stearoyloxyethylthio)ethyl-7-(3-methyl-5-t-butyl-4-hydroxyphenyl)heptanoate, 2-hydroxyethyl-7-(3-methyl-5-t-butyl-4-hydroxyphenyl)propionate, Pentaerythritol Phenolic antioxidants such as rhythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]; sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, and pentaerythrityl tetrakis(3-laurylthiopropionate);Examples of phosphorus-based antioxidants include tridecyl phosphite, triphenyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, 2-ethylhexyl diphenyl phosphite, diphenyl tridecyl phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, distearyl pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, and 2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-N,N-bis[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-ethyl]ethanamine;

[0025] The adhesion promoter is not particularly limited as long as it is a known adhesion promoter and exhibits the effects of the present invention. If necessary, an adhesion promoter may be contained to impart adhesiveness or tackiness (pressure-sensitive adhesiveness). Examples of adhesion promoters include urethane resins, phenolic resins, terpene resins, and silane coupling agents. Among these, silane coupling agents are preferred for imparting adhesiveness.

[0026] The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents such as n-propyltrimethoxysilane, n-propyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane, methoxytri(ethyleneoxy)propyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-isocyanatopropyltrimethoxysilane.

[0027] The amount of other additives added varies depending on the purpose of the composition, but is usually 5% by mass or less of the entire composition excluding inorganic fillers.

[0028] [Method of producing the composition] The thermosetting resin composition of the present invention can be produced by the following method. For example, components (A) and (B) are mixed, simultaneously or separately, while optionally being heated, and then stirred, dissolved, and / or dispersed to obtain a mixture of components (A) and (B). If necessary, a curing accelerator (C) may be added to the mixture of components (A) and (B), followed by stirring, dissolving, and / or dispersing to obtain a mixture of components (A) to (C). Depending on the intended use, at least one of an inorganic filler, a flame retardant, a polymerization initiator, and an ion-trapping agent may be added to and mixed with the mixture of components (A) to (C). Each component may be used alone, or two or more may be used in combination.

[0029] In the method for producing the composition, the apparatus for mixing, stirring, and dispersing is not particularly limited. Specifically, for example, a mortar and pestle mixer equipped with a stirring and heating device, a two-roll mill, a three-roll mill, a ball mill, a planetary mixer, or a mass colloider can be used, and these apparatuses may be used in appropriate combination.

[0030] [Application] The thermosetting resin composition of the present invention gives a cured product having excellent tracking resistance (CTI≧600V) and high heat resistance, and can therefore be suitably used as an adhesive or a semiconductor encapsulant. When used as a semiconductor encapsulant, it is preferable to compound the components in a predetermined composition ratio as described above, mix them sufficiently uniformly using a mixer or the like, melt-mix them using a hot roll, kneader, extruder or the like, cool them down to solidify them, and then pulverize them to an appropriate size. Common molding methods using semiconductor encapsulation materials include transfer molding and compression molding. In transfer molding, a transfer molding machine is used and the molding pressure is 5 to 20 N / mm. 2In the compression molding method, the molding temperature is 120 to 190°C for 30 to 500 seconds, preferably 150 to 185°C for 30 to 180 seconds. In the compression molding method, a compression molding machine is used, and the molding temperature is 120 to 190°C for 30 to 600 seconds, preferably 130 to 160°C for 120 to 300 seconds. In either molding method, post-curing may be performed at 150 to 225°C for 0.5 to 20 hours. [Example]

[0031] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, the number average molecular weight (Mn) was measured by gel permeation chromatography (GPC) using polystyrene as a standard under the following measurement conditions. In the following formula, Me represents a methyl group. [GPC measurement conditions] Developing solvent: tetrahydrofuran (THF) Flow rate: 0.35mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperHZ4000(4.6mmI.D.×15cm×1) TSKgel SuperHZ3000(4.6mmI.D.×15cm×1) TSKgel SuperHZ2000 (4.6mmI.D.×15cm×2) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 5 μL (0.2% by mass THF solution)

[0032] (A) Aliphatic bismaleimide compound [Synthesis Example 1] A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 232.42 g (2.0 mol) of hexamethylenediamine, 411.85 g (4.2 mol) of maleic anhydride, 1200 g of toluene, and 514 g of N-methyl-2-pyrrolidone to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize an amic acid. After that, 192.20 g of methanesulfonic acid was added to the reaction solution, and the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 500 g of ion-exchanged water. The product was then precipitated using heptane and filtered to obtain 357.92 g (65% yield) of the target product ((A-1), Mn 253, melting point 143 °C) as a white solid at room temperature. [ka]

[0033] [Synthesis Example 2] A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 158.35 g (1.0 mol) of trimethylhexanediamine (2,2,4-, 2,4,4-mixture), 205.94 g (2.1 mol) of maleic anhydride, 600 g of toluene, and 257 g of N-methyl-2-pyrrolidone to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. After adding 96.10 g of methanesulfonic acid, the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 300 g of ion-exchanged water. The product (A-2), Mn318, melting point 88 °C) was precipitated using heptane and filtered to obtain 237.81 g (75% yield) of the target product as a white solid at room temperature. [ka]

[0034] [Synthesis Example 3] A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 316.56 g (2.0 mol) of 1,9-nonanediamine, 411.96 g (4.2 mol) of maleic anhydride, 1,200 g of toluene, and 514 g of N-methyl-2-pyrrolidone to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. After that, 192.22 g of methanesulfonic acid was added to the reaction solution, and the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 500 g of ion-exchanged water. The product (A-3), Mn 346, melting point 86 °C) was precipitated using heptane and filtered to obtain 452.09 g (71% yield) of the target product as a brown solid at room temperature. [ka]

[0035] [Synthesis Example 4] A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 340.64 g (2.0 mol) of isophoronediamine (cis-, trans-mixture), 411.96 g (4.2 mol) of maleic anhydride, 870 g of toluene, and 870 g of N-methyl-2-pyrrolidone to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. After that, 192.22 g of methanesulfonic acid was added to the reaction solution, and the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 500 g of ion-exchanged water. The product (A-4), Mn 295, melting point 161 °C) was precipitated using heptane and filtered to obtain 350.48 g (53% yield) of the target product as a white solid at room temperature. [ka]

[0036] [Comparative Synthesis Example 1] A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 176.67 g (2.0 mol) of 1,4-butanediamine, 411.85 g (4.2 mol) of maleic anhydride, 870 g of toluene, and 870 g of N-methyl-2-pyrrolidone to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. After that, 192.25 g of methanesulfonic acid was added to the reaction solution, and the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 500 g of ion-exchanged water. The product (A'-1), Mn 205, melting point 202 °C, was precipitated using heptane and filtered to obtain 348.84 g (70% yield) of the target product as a white solid at room temperature. [ka]

[0037] (A'-2) Maleimide compound represented by the following formula (SLK-6895: manufactured by Shin-Etsu Chemical Co., Ltd., liquid at room temperature) [ka] In the above formula, -C 36 H 70 - represents a hydrocarbon group with 36 carbon atoms derived from dimer acid.

[0038] (B) Epoxy resin (B-1) Biphenyl-type epoxy resin (YX-4000K: manufactured by Mitsubishi Chemical Corporation, melting point 105°C, epoxy equivalent 185) (B-2) Bisphenol A epoxy resin (YL-6810: manufactured by Mitsubishi Chemical Corporation, melting point 45°C, epoxy equivalent 172) (B-3) Dicyclopentadiene epoxy resin (HP-7200: manufactured by DIC Corporation, softening point 57°C, epoxy equivalent 259)

[0039] (C) Curing accelerator (C-1) 2-Ethyl-4-methylimidazole (trade name: 2E4MZ, manufactured by Shikoku Kasei Holdings Co., Ltd.)

[0040] (D) Comparative phenolic resin (D-1) Novolac phenolic resin (trade name: TD-2131, manufactured by DIC Corporation, softening point 78°C, hydroxyl equivalent 110)

[0041] [Examples 1 to 7 and Comparative Examples 1 to 4] The above components were mixed in the amounts (parts by mass) shown in Table 1, poured into a mold, and cured by step curing at 180°C for 1 hour and then at 230°C for 2 hours to obtain a thermosetting resin composition. The resulting resin composition was evaluated as described below. The results are shown in Table 1. Note that the bismaleimide compound (A'-1) shown in Comparative Example 1 in Table 1 has a melting point in the temperature range (approximately 200°C) where the curing reaction proceeds. Therefore, when the components of the composition of Comparative Example 1 were mixed, the melting of the bismaleimide compound (A'-1) and the curing reaction proceeded simultaneously, making it impossible to obtain a uniform cured product. In Table 1, each bismaleimide compound of component (A) is abbreviated as "BMI compound."

[0042] <Glass transition temperature (Tg) measurement> The above components were mixed in the amounts (parts by mass) listed in Table 1, poured into a mold, and cured by step curing at 180°C for 1 hour and then at 230°C for 2 hours to obtain a 10 mm x 4 mm x 35 mm thick test piece. The storage modulus (MPa) of the test piece in the 25°C to 400°C range was measured using a TA Instruments DMA-800, and the glass transition temperature (Tg) was determined from the graph plotting Tan δ values ​​derived from the storage modulus and loss modulus values.

[0043] <5% weight loss temperature (Td5) measurement> The above components were mixed in the amounts (parts by mass) listed in Table 1, poured into a mold, and cured by step curing at 180°C for 1 hour and then at 230°C for 2 hours. The cured product was crushed with a hammer to obtain micro-test pieces. The weight loss of the micro-test pieces was measured in the range of 25°C to 500°C using a Rigaku Thermo plus EVO2. The temperature at which a 5% weight loss from the weight before the start of the measurement was observed in the micro-test pieces was defined as Td5.

[0044] <Tracking resistance (CTI) measurement> The above components were mixed in the amounts (parts by mass) listed in Table 1, poured into a mold, and cured by step curing at 180°C for 1 hour and then at 230°C for 2 hours to obtain a disk-shaped cured product with a thickness of 3 mm and a diameter of 50 mm. Tracking resistance measurements were performed using the cured product according to the method of JIS C 2134:2021 (IEC 60112). Tracking resistance voltage was measured as the maximum voltage at which none of the cured products broke down even when 50 or more drops of a 0.1% aqueous solution of ammonium chloride were dropped onto the cured product, with n = 5 samples measured. The upper limit was 600 V.

[0045] <Bending strength measurement> The above components were mixed in the amounts (parts by mass) shown in Table 1, poured into a mold, and cured by step curing at 180°C for 1 hour and then at 230°C for 2 hours to obtain a test piece measuring 100 mm x 10 mm x 4 mm thick. The test piece was subjected to a three-point bending test using an autograph manufactured by Shimadzu Corporation in accordance with JIS K 6911:2006, and the bending strength was calculated.

[0046] [Table 1] The results in Table 1 demonstrate that the cured products of the resin compositions of Examples 1 to 7, which contained an aliphatic bismaleimide compound in which the group between the two maleimide groups was a divalent aliphatic hydrocarbon group having 5 to 12 carbon atoms, all had excellent tracking resistance and high heat resistance.

Claims

1. (A) an aliphatic bismaleimide compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), A is a divalent aliphatic hydrocarbon group having 5 to 12 carbon atoms.) and (B) Epoxy resin having two or more epoxy groups in one molecule A thermosetting resin composition comprising: A thermosetting resin composition in which the component (A) accounts for 20 to 95 mass % of the total of the components (A) and (B).

2. 2. The thermosetting resin composition according to claim 1, wherein in the formula (1), A is a divalent chain aliphatic hydrocarbon group having 5 to 12 carbon atoms.

3. The thermosetting resin composition according to claim 1, further comprising (C) a curing accelerator.

4. 4. The thermosetting resin composition according to claim 3, wherein the component (C) comprises at least one selected from the group consisting of an imidazole-based curing accelerator, an organic phosphorus-based curing accelerator, and a tertiary amine-based curing accelerator.

5. A semiconductor encapsulant comprising the thermosetting resin composition according to any one of claims 1 to 4.

6. 6. The semiconductor encapsulant according to claim 5, wherein the semiconductor is a power semiconductor.

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