Liquid resin composition and resin-encapsulated power module

Abstract

This invention provides a liquid resin composition for use in encapsulating power modules by casting, which offers an excellent balance between high-temperature storage characteristics and flame retardancy. [Solution] A liquid resin composition used for sealing a power module by casting, comprising a power module substrate on which a circuit layer is formed, and a power semiconductor element mounted on the circuit layer of the power module substrate, The liquid resin composition, epoxy resin, inorganic fillers, and Contains flame retardant, The flame retardant is a halogenated compound having a melting point of 250°C or higher and 600°C or lower. Liquid resin composition.

Description

Technical Field

[0001] The present invention relates to a liquid resin composition and a resin-sealed power module. More specifically, the present invention relates to a liquid resin composition used for sealing a power module by a casting method, and a resin-sealed power module sealed with the liquid resin composition.

Background Art

[0002] Conventionally, an epoxy resin composition that is liquid at room temperature has been used for sealing semiconductor elements. Examples of such conventional liquid epoxy resin compositions include epoxy resins such as bisphenol type epoxy resins and alicyclic epoxy resins, curing agents such as acid anhydrides and phenol novolacs, curing accelerators such as imidazoles, and inorganic fillers such as fused silica. In addition, in order to ensure the flame retardancy of the liquid epoxy resin composition as a sealing material, halogen-based compounds, antimony compounds, phosphorus-based compounds, metal hydrate compounds, etc. are used. Among these, the means of using a brominated epoxy resin, which is a halogen-based compound, and antimony trioxide, which is an antimony compound, in combination is effective for ensuring flame retardancy and has been put into practical use. For example, Patent Document 1 describes a liquid epoxy resin composition at room temperature containing an epoxy resin, a curing agent, a curing accelerator, a silane coupling agent, an inorganic filler, and antimony trioxide, and an epoxy resin composition containing a brominated epoxy resin as the epoxy resin.

[0003] However, when a semiconductor device sealed with a conventional epoxy resin composition is stored at a high temperature, brominated compounds thermally decomposed from these flame retardant components may be released, which may impair the reliability of the bonding portion of the semiconductor element.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Further investigation by the inventors revealed that by using a specific halogenated compound as a flame retardant in a flame-retardant epoxy resin composition, the flame retardancy and high-temperature storage properties of the cured product can be improved, thus completing the present invention.

[0006] The present invention provides an epoxy resin composition that exhibits excellent high-temperature storage properties and a good balance between high-temperature storage properties and flame retardancy, and a highly reliable resin-encapsulated power module sealed using this composition. [Means for solving the problem]

[0007] According to the present invention, the following liquid resin composition and resin-encapsulated power module are provided. [1] A liquid resin composition used for sealing a power module by casting, the power module comprising a power module substrate on which a circuit layer is formed and a power semiconductor element mounted on the circuit layer of the power module substrate, The liquid resin composition, epoxy resin, inorganic fillers, and Contains flame retardant, The flame retardant is a halogenated compound having a melting point of 250°C or higher and 600°C or lower. Liquid resin composition. [2] The liquid resin composition described in [1], The flame retardant is a halogenated compound having a 5% decomposition temperature of 300°C to 500°C, comprising a liquid resin composition. [3] A liquid resin composition according to [1] or [2], The flame retardant is a halogenated compound having a melting point of 300°C or more and 500°C or less, in a liquid resin composition. A liquid resin composition according to any of [4] [1] to [3], The flame retardant is a liquid resin composition which is a brominated compound. A liquid resin composition according to any of [5] [1] to [4], The flame retardant is a compound represented by formula (1) and a compound represented by formula (2): [ka]

[0008] [ka] A liquid resin composition comprising at least one selected from the following. A liquid resin composition according to any of [6] [1] to [5], The epoxy resin is a liquid resin composition containing an alicyclic epoxy resin. A liquid resin composition as described in [7] [6], The epoxy resin is a liquid resin composition further comprising a liquid bisphenol A type epoxy resin or a liquid bisphenol F type epoxy resin. A liquid resin composition according to any one of [8] [1] to [7], A liquid resin composition in which the flame retardancy of the cured product is V-0, as measured in accordance with the UL standard UL-94 vertical method (vertical combustion test). A liquid resin composition according to any of [9] [1] to [8], A two-component liquid resin composition.

[10] A resin-encapsulated power module comprising a power module substrate on which a circuit layer is formed, a power semiconductor element mounted on the circuit layer of the power module substrate, and a sealing material covering the power module substrate and the power semiconductor element, A resin-encapsulated power module wherein the encapsulating material consists of a cured product of a liquid resin composition described in any of [1] to [9]. [Effects of the Invention]

[0009] According to the present invention, there is provided a liquid resin composition used for encapsulating a power module by a casting method, which has an excellent balance between high-temperature storage characteristics and flame retardancy. Further, according to the present invention, there is provided a resin-encapsulated power module encapsulated using the liquid resin composition and having excellent reliability.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described. In this specification, a numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a certain stepwise numerical range can be arbitrarily combined with the upper limit value or the lower limit value of another stepwise numerical range. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" means that either one of A and B may be included, or both may be included. The materials exemplified in this specification can be used alone or in combination of two or more without particular notice. In this specification, the content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition, unless otherwise specified when there are a plurality of substances corresponding to each component in the composition.

[0011] [Liquid Resin Composition] The resin composition of the present embodiment is a liquid resin composition for casting, which is used for encapsulating a power semiconductor device. More specifically, the resin composition of the present embodiment is used for encapsulating a power module including a power module substrate on which a circuit layer is formed and a power semiconductor device mounted on the circuit layer of the power module substrate by a casting method. The liquid resin composition for casting a power module of the present embodiment (which may be simply referred to as "resin composition" in this specification) contains (A) an epoxy resin, (B) an inorganic filler, and (C) a flame retardant. In the present embodiment, the flame retardant is a halogenated compound having a melting point of 250°C or higher and 600°C or lower.

[0012] The resin composition of this embodiment contains a halogenated compound having a melting point of 250°C to 600°C as a flame retardant. By including such a flame retardant, the cured product of the resin composition of this embodiment exhibits high flame retardancy and excellent high-temperature storage properties.

[0013] The components used in the resin composition of this embodiment will be described in detail below. (Epoxy resin (A)) The epoxy resin (A) incorporated into the resin composition of this embodiment can be an epoxy resin commonly used in the field. Specific examples of epoxy resin (A) include, for example, bisphenol-type epoxy resins such as novolac-type epoxy resin, bisphenol A-type epoxy resin, and bisphenol F-type epoxy resin; aromatic glycidylamine-type epoxy resins such as N,N-diglycidylaniline, N,N-diglycidyltoluidine, diaminodiphenylmethane-type glycidylamine, and aminophenol-type glycidylamine; hydroquinone-type epoxy resin; biphenyl-type epoxy resin; stilbene-type epoxy resin; triphenolmethane-type epoxy resin; and triphenolpropane-type epoxy resin. Examples include epoxy resins; alkyl-modified triphenolmethane type epoxy resins; triazine nucleus-containing epoxy resins; dicyclopentadiene-modified phenol type epoxy resins; naphthol type epoxy resins; naphthalene type epoxy resins; phenol aralkyl type epoxy resins having a phenylene and / or biphenylene skeleton; naphthol aralkyl type epoxy resins having a phenylene and / or biphenylene skeleton; and alicyclic epoxy resins such as vinylcyclohexene dioxide, dicyclopentadiene oxide, and alicyclic diepoxy adipade.

[0014] In a preferred embodiment, the resin composition of the present invention comprises an alicyclic epoxy resin as the epoxy resin (A). Preferably, an alicyclic epoxy resin that is liquid at 25°C is used as the alicyclic epoxy resin, and such liquid alicyclic epoxy resins include vinylcyclopentadiene dioxide, vinylcyclohexene monodioxide, vinylcyclohexene dioxide, dicyclopentadiene oxide, 3,4-epoxy-1-[8,9-epoxy-2,4-dioxaspiro[5,5]undecane-3-yl]cyclohexane, and other epoxy-[epoxy-oxaspiroC 8-15 Alkyl]-CycloC 5-12 Epoxy C such as alkanes, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, and 4,5-epoxycyclooctylmethyl-4',5'-epoxycyclooctanecarboxylate. 5-12 Cycloalkyl C 1-3 Alkyl-epoxy C 5-12 Cycloalkanecarboxylates, bis(2-methyl-3,4-epoxycyclohexylmethyl) adipates, etc. 1-3 Alkyl epoxy C 5-12 Cycloalkyl C 1-3 Examples include alkyl)dicarboxylates. A commercially available 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate is Daicel Corporation's product, trade name: Celoxide #2021P (epoxy equivalent: 128-140), which is preferably used.

[0015] The resin composition of the present invention, by containing such an alicyclic epoxy resin, has a cured product with a high glass transition temperature of 200°C or higher, and therefore possesses sufficient heat resistance for use as a encapsulant for power modules.

[0016] When the resin composition of the present invention contains an alicyclic epoxy resin, the amount of alicyclic epoxy resin contained in epoxy resin (A) is, for example, 70% by mass or more, preferably 75% by mass or more, and more preferably 80% by mass or more, relative to the total epoxy resin (A).

[0017] In a preferred embodiment, the epoxy resin (A) includes, in addition to the alicyclic epoxy resin, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. By using these epoxy resins, the heat resistance of the cured product of the resulting resin composition can be further improved, and the insulation reliability can be enhanced.

[0018] If the epoxy resin (A) contains a bisphenol A type epoxy resin or a bisphenol F type epoxy resin, the amount thereof is, for example, 30% by mass or less, preferably 25% by mass or less, and more preferably 20% by mass or less, relative to the total epoxy resin (A).

[0019] The epoxy resin (A) may include other epoxy resins different from the epoxy resins described above, as long as they do not impair the physical properties of the cured resin composition, such as heat resistance and insulation. Examples of other epoxy resins include bisphenol type epoxy resins such as bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol M type epoxy resin (4,4'-(1,3-phenylenediisopridiene)bisphenol type epoxy resin), bisphenol P type epoxy resin (4,4'-(1,4-phenylenediisopridiene)bisphenol type epoxy resin), and bisphenol Z type epoxy resin (4,4'-cyclohexydiene bisphenol type epoxy resin); phenol novolac type epoxy resin, cresol novolac type epoxy resin, trisphenol group methane type novolac type epoxy resin, and tetraphenol group ethane type novolac type epoxy resin. Examples of epoxy resins include novolac-type epoxy resins having a condensed ring aromatic hydrocarbon structure; biphenyl-type epoxy resins; arylalkylene-type epoxy resins such as xylylene-type epoxy resins and biphenylaralkyl-type epoxy resins; naphthalene-type epoxy resins such as naphthylene ether-type epoxy resins, naphthol-type epoxy resins, naphthalenediol-type epoxy resins, bifunctional to tetrafunctional epoxy-type naphthalene resins, binaphthyl-type epoxy resins, and naphthalenearalkyl-type epoxy resins; anthracene-type epoxy resins; phenoxy-type epoxy resins; dicyclopentadiene-type epoxy resins; norbornene-type epoxy resins; adamantane-type epoxy resins; and fluorene-type epoxy resins. When using these epoxy resins, the amount is, for example, 10% by mass or less, preferably 5% by mass or less, relative to the total epoxy resin (A).

[0020] The amount of epoxy resin (A) in the resin composition of this embodiment is, for example, 2% to 30% by mass, preferably 4% to 25% by mass, relative to the total amount of the resin composition. The amount of epoxy resin (A) in the resin composition refers to the total amount of the alicyclic epoxy resin described above and, if necessary, bisphenol A type epoxy resin or bisphenol F type epoxy resin, or other epoxy resins.

[0021] (Inorganic filler (B)) The resin composition of this embodiment includes an inorganic filler (D). Examples of inorganic fillers (B) include silica fillers such as quartz, fumed silica, precipitated silica, anhydrous silicic acid, fused silica, crystalline silica, and ultrafine amorphous silica, as well as alumina, zircon, iron oxide, zinc oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, silicon carbide, glass fiber, glass flakes, alumina fiber, carbon fiber, mica, graphite, carbon black, ferrite, graphite, diatomaceous earth, white clay, clay, talc, aluminum hydroxide, magnesium hydroxide, calcium carbonate, manganese carbonate, magnesium carbonate, barium sulfate, potassium titanate, calcium silicate, inorganic balloons, and silver powder. These may be used individually or in combination of two or more. The inorganic filler may also be subjected to surface treatment. Examples of surface treatments include alkylation treatment, trimethylsilylation treatment, silicone treatment, and treatment with silane coupling agents, but are not particularly limited.

[0022] By using an inorganic filler (B), the viscosity of the resulting resin composition can be adjusted to an appropriate range, and various physical properties of the cured resin composition, such as strength, hardness, elastic modulus, thermal expansion coefficient, thermal conductivity, heat dissipation, and electrical properties, can be improved.

[0023] In particular, silica filler is preferred as the inorganic filler (B). Silica filler refers to silica-based fillers such as quartz, fumed silica, precipitated silica, anhydrous silicic acid, fused silica, crystalline silica, and ultrafine amorphous silica. In typical resin compositions, increasing the amount of filler added leads to a significant increase in the viscosity of the resin composition containing it. From the viewpoint of viscosity control, a spherical shape is preferred over fibrous or irregular shapes. Here, "spherical" means a nearly spherical shape that may be a perfect sphere, an ellipse, or an egg shape, and specifically, an aspect ratio (ratio of major axis to minor axis) of 1.3 or less is usually preferred, preferably 1.2 or less, and more preferably 1.1 or less. Furthermore, from a formulation standpoint, it is preferable that the filler surface has hydroxyl groups. The presence of hydroxyl groups improves the polarity of the filler surface, making it easier to mix in organic polymers, which have higher polarity compared to inorganic materials. Furthermore, it is possible to increase the amount of filler added by controlling the particle size distribution. In other words, a higher filling density can be obtained by mixing fillers with different particle sizes. The average particle size of the filler is measured using a Particle Size Analyzer (CILAS 1064), and is preferably 0.1 μm or larger, more preferably 1 μm or larger. It is also preferably 100 μm or smaller, and more preferably 50 μm or smaller.

[0024] The amount of inorganic filler (B) in the resin composition of this embodiment is, for example, 65% to 85% by mass relative to the entire resin composition. The lower limit of the amount of inorganic filler (B) is preferably 68% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more, relative to the entire resin composition. The upper limit of the amount of inorganic filler (B) is preferably 82% by mass or less, and more preferably 80% by mass or less, relative to the entire resin composition. By using inorganic filler (B) in an amount within the above range, the resulting resin composition has a viscosity suitable for casting, and therefore excellent casting workability, and the cured product of the resin composition has low thermal expansion and high heat resistance. This makes it possible to improve the curability of the resin composition.

[0025] (Flame retardant (C)) The resin composition of this embodiment contains a flame retardant (C), the flame retardant (C) containing as an essential component a halogenated compound (hereinafter referred to as "flame retardant (c1)") having a 5% decomposition temperature of 300°C to 500°C. Preferably, the flame retardant (c1) is a halogenated compound having a 5% decomposition temperature of 300°C to 500°C and a melting point of 300°C to 500°C. In a more preferred embodiment, the halogenated compound is a brominated compound. Examples of such flame retardants (c1) include ethylenebistetrabromophthalimide (compound of formula (1)) and decabromodiphenylethane (compound of formula (2)). [ka]

[0026] [ka]

[0027] The amount of flame retardant (c1) in the resin composition of this embodiment is, for example, 1% to 20% by mass relative to the entire resin composition. The lower limit of the amount of flame retardant (c1) is preferably 2% by mass or more, and more preferably 3% by mass or more, relative to the entire resin composition. The upper limit of the amount of flame retardant (c1) is preferably 15% by mass or less, and more preferably 10% by mass or less, relative to the entire resin composition. By using the flame retardant (c1) in an amount within the above range, the resulting resin composition has excellent flame retardancy and improved high-temperature storage characteristics.

[0028] (Other flame retardants) Other flame retardants that can be used in the present invention (hereinafter referred to as "flame retardant (c2)") include boron-containing compounds, chlorine compounds, inorganic compounds, and the like. Examples of boron-containing compounds include boric acid (such as orthoboric acid and metaboric acid), borates (such as alkali metal borates like sodium tetraborate, alkaline earth metal salts like barium metaborate, and transition metal salts like zinc borate), condensed boric acid (salts) (such as pyroboric acid, tetraboric acid, pentaboric acid, octaboric acid, or their metal salts), and boron nitride. These boron-containing compounds may also be hydrated (for example, borax, which is hydrated sodium tetraborate).

[0029] Examples of chlorine compounds include chlorinated paraffin, chlorinated naphthalene, tris(chloroethyl) phosphate, and tris(2,3-dichloropropyl) phosphate. Examples of inorganic compounds include antimony trioxide, antimony pentoxide, aluminum hydroxide, magnesium hydroxide, boehmite, and graphite. Other flame retardants (c2) may be used individually or in combination of two or more types.

[0030] The amount of other flame retardant (c2) in the resin composition of this embodiment is, for example, 0.5% to 10% by mass relative to the entire resin composition. The lower limit of the amount of flame retardant (c2) is preferably 0.8% by mass or more, and more preferably 1% by mass or more, relative to the entire resin composition. The upper limit of the amount of flame retardant (c2) is preferably 8% by mass or less, and more preferably 5% by mass or less, relative to the entire resin composition. By using the flame retardant (c2) in an amount within the above range, the flame retardancy of the resulting resin composition can be further improved.

[0031] (Acid anhydride (D)) The resin composition of this embodiment may contain an acid anhydride (D). The acid anhydride (D) acts as a curing agent for the epoxy resin (A). Examples of usable acid anhydrides (D) include dodecenyl succinic anhydride, polyadipic anhydride, polyazelaic anhydride, polysebacic anhydride, poly(ethyl octadecanediic acid) anhydride, poly(phenylhexadecanedioic acid) anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhymic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexendicarboxylic acid anhydride, phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride. Examples include acids, benzophenonetetracarboxylic anhydride, ethylene glycol bistrimellitate, hetic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride (methyl-5-norbornene-2,3-dicarboxylic anhydride), methylhymic anhydride (methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride), 4-methylcyclolohexane-1,2-dicarboxylic anhydride, and 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexane-1,2-dicarboxylic anhydride. In particular, as the acid anhydride (B), it is preferable to use methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl-5-norbornene-2,3-dicarboxylic acid anhydride, or methylcyclohexane-1,2-dicarboxylic acid anhydride, which are liquid at 25°C, because they mix easily and uniformly with other components such as epoxy resin (A). In particular, it is more preferable to use methyl-5-norbornene-2,3-dicarboxylic acid anhydride, methylcyclohexane-1,2-dicarboxylic acid anhydride, and methyltetrahydrophthalic anhydride. Furthermore, when using methyltetrahydrophthalic anhydride, it is preferable to use one with a viscosity of 30 to 50 mPa·s at 25°C. By using such an acid anhydride, it is possible to further reduce the viscosity of the resulting resin composition. Examples of commercially available acid anhydrides include the HN series manufactured by Showa Denko Materials Co., Ltd. Acid anhydride (D) may be used alone or in combination of two or more types.

[0032] When the resin composition of this embodiment contains acid anhydride (D), the amount of acid anhydride (D) in the resin composition is preferably 5% to 50% by mass, and more preferably 10% to 40% by mass or less, relative to the entire resin composition, from the viewpoint of workability and curability. Furthermore, the ratio of the total number of functional groups of the acid anhydride to the total number of epoxy groups of the epoxy resin (A) is preferably 0.7 to 1.2, and more preferably 0.8 to 1.1. By using acid anhydride (D) in an amount within the above range, the mechanical strength and insulating properties of the cured resin composition can be improved.

[0033] (Curing accelerator (E)) The resin composition of this embodiment may also contain a curing accelerator (E). The curing accelerator (E) has the effect of promoting the reaction between the epoxy resin (A) and the acid anhydride (D), which is a curing agent. Examples of usable curing accelerators (E) include tertiary amines, quaternary ammonium salts, imidazoles, organophosphines, Lewis acid catalysts, etc. Among these, quaternary ammonium salts are also preferably used.

[0034] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, and benzyldimethylamine.

[0035] Examples of quaternary ammonium salts include diazabicycloundecene organic salts such as DBU [1,8-diazabicyclo[5.4.0]undecene-7] octylate (manufactured by Sunapro Co., Ltd., trade name: SA102), DBN [1,5-diazabicyclo[4.3.0]-5-nonene], quaternary ammonium salts which are salts of tertiary amines and carboxylic acids (manufactured by Sunapro Co., Ltd., trade name: U-CAT2313), octadecyltrimethylammonium chloride (manufactured by NOF Corporation, trade name: Nissan Cation), and tetraalkyl (each alkyl group has 1 to 18 carbon atoms) ammonium salts (e.g., tetraethylammonium bromide, tetrabutylammonium bromide, tetraalkylammonium carboxylate (carboxylic acid has 1 to 12 carbon atoms)).

[0036] Examples of imidazoles include 1-benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, and 1-benzyl-2-phenylimidazole.

[0037] Examples of organic phosphines include triphenylphosphine, triphenylphosphine-triphenylborate, tris(p-methoxyphenyl)phosphine, and tetraphenylphosphonium-tetraphenylborate.

[0038] Examples of Lewis acid catalysts include boron trifluoride amine complexes, boron trichloride amine complexes, and boron trifluoride ethylamine complexes. These may be used individually or in combination of two or more types.

[0039] When the resin composition of this embodiment contains a curing accelerator (E), the amount of curing accelerator (E) in the resin composition is, for example, 0.03% by mass or more, preferably 0.05% by mass or more, and more preferably 0.08% by mass or more, relative to the entire resin composition. This improves the curability of the resin composition. On the other hand, the upper limit of the curing accelerator (E) content is, for example, 1% by mass or less, preferably 0.8% by mass or less, and more preferably 0.5% by mass or less, relative to the entire resin composition. This improves the casting workability.

[0040] (Anti-settling agent (F)) The resin composition of this embodiment may contain a settling inhibitor (F). By using a settling inhibitor (F), the settling of the inorganic filler (B) in the resin composition can be suppressed. Examples of settling inhibitors (F) that can be used include fine silica particles, asbestos powder, needle-shaped magnesium, polyhydroxycarboxylic acid esters, synthetic waxes, ultrafine settling calcium carbonate, clay, talc, organic bentonite, metal soaps, plant-based polymerized oils, and oxidized polyethylene surfactants.

[0041] When the resin composition of this embodiment contains a settling inhibitor (F), the amount of settling inhibitor (F) in the resin composition is, for example, 0.01% to 1.00% by mass relative to the entire resin composition. The lower limit of the amount of settling inhibitor (F) is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more, relative to the entire resin composition. The upper limit of the amount of settling inhibitor (F) is preferably 0.80% by mass or less, and more preferably 0.50% by mass or less, relative to the entire resin composition. By using the settling inhibitor (F) in an amount within the above range, the resulting resin composition can suppress filler settling during storage and curing, and maintain viscosity and fluidity suitable for casting workability.

[0042] (Coupling agent) The resin composition of this embodiment may contain a coupling agent. By using a coupling agent, the compatibility between the epoxy resin (A) and the inorganic filler (B) can be improved. Examples of coupling agents that can be used include silane coupling agents such as epoxysilane, aminosilane, ureidosilane, and mercaptosilane.

[0043] Examples of the epoxysilanes mentioned above include γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Examples of aminosilanes include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-(6-aminohexyl)3-aminopropyltrimethoxysilane, and N-(3-(trimethoxysilylpropyl)-1,3-benzenedimethanane). Examples of ureidosilanes include γ-ureidopropyltriethoxysilane and hexamethyldisilazane. These may be used individually or in combination of two or more.

[0044] The lower limit of the coupling agent content is, for example, 0.05% by mass or more, preferably 0.02% by mass or more, and more preferably 0.05% by mass or more, relative to the entire resin composition. The upper limit of the coupling agent content is, for example, 1% by mass or less, preferably 0.8% by mass or less, and more preferably 0.6% by mass or less, relative to the entire resin composition. This suppresses a decrease in the interfacial strength between the epoxy resin (A) and the inorganic filler (B), and the resulting resin composition has excellent durability.

[0045] (Other additives) The resin composition of this embodiment may optionally contain a coloring agent such as carbon black, an antifoaming agent such as a silicone antifoaming agent, and the like.

[0046] (Method for producing liquid resin composition) The method for producing the liquid resin composition of this embodiment will be described in detail. The resin composition of this embodiment can be manufactured by conventional methods by adding the above-mentioned components, namely epoxy resin (A), inorganic filler (B), and flame retardant (C), as well as, optionally, acid anhydride (D), curing accelerator (E), settling inhibitor (F), and other components, and thoroughly mixing and stirring them.

[0047] In one embodiment, the resin composition of the present invention is a two-component type and can be obtained by mixing and / or kneading a main component and a curing agent. More specifically, for example, the main component is produced by mixing an epoxy resin (A) with a portion of an inorganic filler (B), a flame retardant (C), a settling inhibitor (F), and various components that are added as needed. The curing agent is produced by mixing an acid anhydride (D) as a curing agent with a curing accelerator (E), the remainder of the inorganic filler (B), a settling inhibitor (F), and various components that are added as needed. Then, the main component and the curing agent can be mixed and / or kneaded using a mixer or other mixing machine, or a kneader or roll kneader to obtain a liquid resin composition.

[0048] (Physical properties of liquid resin compositions) The resin composition of this embodiment is characterized by being liquid at 25°C, which allows for easy casting and prevents excessive heat curing. The viscosity of the liquid resin composition of this embodiment containing the above components at 25°C is 75 Pa·s or less, preferably 70 Pa·s or less, more preferably 65 Pa·s or less, even more preferably 60 Pa·s or less, and still more preferably 55 Pa·s or less. The lower limit of the viscosity of the resin composition at 25°C is not particularly limited, but for example, it is 5 Pa·s or more. A liquid resin composition having a viscosity within the above range has excellent casting workability.

[0049] The liquid resin composition of this embodiment preferably has a flow distance of 20 mm or more, more preferably 25 mm or more, even more preferably 30 mm, and still more preferably 35 mm or more, under the following conditions. The upper limit of the flow distance of the resin composition is, for example, 80 mm or less. A liquid composition having a flow distance within this range has excellent casting workability. (Conditions) 0.05 ml of the liquid resin composition of this embodiment is applied to a glass plate so that the diameter of the liquid resin composition is 1 cm or less. Then, the glass plate is held at an inclination angle of 45° and at a temperature of 60°C for 3 minutes, and the distance the liquid resin composition flows during that time is defined as the flow distance (mm).

[0050] (Method for curing resin compositions) The heating method used to cure the resin composition of this embodiment is not particularly limited, and conventionally known methods such as hot air circulation heating, infrared heating, and high-frequency heating can be employed. The heat treatment conditions are not particularly limited as long as they can bring the resin composition to the desired cured state, but for example, a temperature of 100°C to 200°C is applied.

[0051] (Physical properties of cured resin compositions) The cured product of the liquid resin composition of this embodiment has a glass transition temperature of 180°C or higher, preferably 190°C or higher, more preferably 200°C or higher, even more preferably 205°C or higher, and particularly preferably 210°C or higher. As a result, the cured product of the liquid resin composition has excellent heat resistance and can therefore be suitably used as a encapsulant for power modules. The upper limit of the glass transition temperature of the cured product of the resin composition of this embodiment is, for example, 250°C or lower.

[0052] The cured product of the liquid resin composition of this embodiment has a linear expansion coefficient of 25 ppm / K or less, preferably 20 ppm / K or less, and more preferably 18 ppm / K or less. The cured product of the liquid resin composition has excellent crack resistance. The lower limit of the linear expansion coefficient of the cured product of the liquid resin composition of this embodiment is, for example, 10 ppm / K or more.

[0053] The flexural modulus of the cured liquid resin composition of this embodiment at 25°C is, for example, 20 GPa or less, preferably 18 GPa or less, and more preferably 16 GPa or less. The lower limit of the flexural modulus of the cured resin composition of this embodiment at 25°C is, for example, 10 GPa or more.

[0054] [Power Module] The cured resin composition of this embodiment has a low coefficient of thermal expansion at high temperatures and high heat resistance, making it suitable for use as a encapsulant for power modules. Examples of power modules include rectifiers, frequency converters, regulators, and inverters. The resin composition of the present invention is fluid, and therefore has good casting workability. Furthermore, the cured resin composition of this embodiment has a low coefficient of linear expansion, making it suitable for use in power modules of a wide range of sizes. It can be used in power modules for home appliances, computers, etc., as well as in large power modules for automobiles, railway vehicles, and substation control.

[0055] The power module of this embodiment can be obtained by pouring the above-mentioned resin composition onto a power semiconductor element mounted on a power module substrate on which a circuit layer has been formed, so as to cover the substrate and the power semiconductor element, and then curing it. It is preferable to vacuum degas the resin composition during and / or before and after casting. Vacuum degassing removes air and other particles contained in the resin composition, making it possible to obtain a resin-sealed power module with fewer voids in the cured epoxy resin composition. The power module of this embodiment has excellent reliability because it is equipped with the cured resin composition described above as a encapsulant.

[0056] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0057] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto. No.

[0058] The raw materials used in the examples and comparative examples are as follows: <(A) Epoxy resin> • Epoxy resin 1: Alicyclic epoxy resin (manufactured by Daicel Corporation, Celoxide 2021P) <(B) Inorganic filler> • Inorganic filler 1: Spherical fused silica (Denka Corporation, FB-950, volume-average particle size 23 μm) (C) Flame retardant • Flame retardant 1: Ethylene bistetrabromophthalimide (compound of formula (1) above) (manufactured by Shouguang Weidong Chemical Co., Ltd., RDT-5, melting point: 455℃, 5% decomposition temperature: 410℃) • Flame retardant 2: Decabromodiphenylethane (compound of formula (2) above) (manufactured by Tokyo Chemical Industry Co., Ltd., 1,2-bis(2,3,4,5,6-pentabromophenyl)ethane, melting point: 352℃, 5% decomposition temperature: 390℃) • Flame retardant 3: Brominated epoxy resin (DIC Corporation, EPICLON 153, no melting point (liquid at room temperature)) • Flame retardant 4: Tris(tribromophenoxy)triazine (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., SR-245, melting point: 232℃, 5% decomposition temperature: 380℃) • Flame retardant 5: Antimony trioxide (manufactured by Nippon Seikou Co., Ltd., PATOX-K) <(D) Acid anhydride (hardener)> • Acid anhydride 1: Methylnadic acid anhydride (manufactured by Showa Denko Materials, MHAC-P) <(E) Curing accelerator> • Curing accelerator 1: Octylate of DBU [1,8-diazabicyclo[5.4.0]undecene-7] (manufactured by Sunapro Co., Ltd., product name: SA102) <(F) Settlement inhibitor> • Settlement inhibitor 1: Organic bentonite (Hojun Co., Ltd., Esben N-400) <Other additives> • Coloring agent 1: Carbon black (manufactured by Mitsubishi Chemical Corporation, Carbon #5) • Coupling agent 1: Epoxysilane coupling agent (Momentive Performance Materials, A-187) • Defoaming agent 1: Silicone defoaming agent (Shin-Etsu Chemical Co., Ltd., KS603)

[0059] (Examples 1-2, Comparative Examples 1-3) <Manufacturing of liquid resin composition> Main component (I) was obtained by mixing the components shown in Table 1 under "Main component" in the amounts shown in Table 1. Separately, curing agent (II) was obtained by mixing the components shown in Table 1 under "Curing agent" in the amounts shown in Table 1. A liquid resin composition was prepared by mixing 100 parts by mass of the above main component (I) and 100 parts by mass of curing agent (II).

[0060] <Evaluation of physical properties of resin compositions> The following physical properties were measured for the main component (I) obtained in each example and comparative example, as well as for the liquid resin composition obtained by mixing the main component (I) with the curing agent (II). The results are shown in Table 1. (Viscosity at 25°C) The viscosity of the main component (I) and the liquid resin composition was measured using an E-type viscometer with rotor No. 4, under the conditions of a rotation speed of 10 rpm, a temperature of 25°C, and a measurement time of 1 minute. The results are shown in Table 1.

[0061] <Evaluation of physical properties of cured resin products> The following physical properties were measured for the cured products obtained by curing the liquid resin compositions obtained in each example and comparative example. (Glass transition temperature) Each liquid resin composition was poured into an aluminum cup and cured at 160°C for 1 hour, followed by 180°C for 2 hours. After slow cooling to room temperature, test specimens were cut to dimensions of 10 mm × 5 mm × 5 mm. These specimens were measured using a thermomechanical analyzer (Hitachi High-Tech Science, TMA7100) under the conditions of a measurement temperature range of 0°C to 320°C and a heating rate of 10°C / min. The glass transition temperature (°C) was then calculated from these measurement results. A higher glass transition temperature indicates better heat resistance of the cured product.

[0062] (High-temperature storage characteristics) Each example of the liquid resin composition was poured into a mold with a hole (width 3.0 mm, length 140 mm, height 240 mm) and cured at 160°C for 1 hour, followed by 180°C for 2 hours. After slow cooling to room temperature, test specimens were cut to dimensions of 50 mm × 50 mm × 3 mm. The obtained test specimens were placed in an oven at 220°C and left to stand for 192 hours. After being removed from the oven and cooled, their appearance was visually inspected and evaluated based on the following evaluation criteria. Test specimens that show no external abnormalities can be considered to have excellent high-temperature storage properties for cured products. A: No external abnormalities such as blisters or cracks of 1 mm or more are observed. B: Those exhibiting external abnormalities such as blisters or cracks measuring 1 mm or more. Furthermore, for test specimens that did not show any external abnormalities, they were again placed in a 220°C oven and left to stand until external abnormalities such as blistering or cracking occurred, and the time taken for such abnormalities to occur was recorded. The results are shown in Table 1. The longer the time until external abnormalities occur, the better the high-temperature storage characteristics of the cured material can be considered to be.

[0063] (Flame retardant) Each example of the liquid resin composition was poured into a mold with a hole (1.5 mm wide, 100 mm long, 140 mm high) and cured at 160°C for 1 hour, followed by 180°C for 2 hours. After slow cooling to room temperature, the samples were cut to dimensions of 1.5 mm × 12.5 mm × 125 mm and evaluated by burning time using the UL-94 vertical test. A maximum burning time of 10 seconds or less and a total burning time of 50 seconds or less is classified as "V-0", a maximum burning time of more than 10 seconds but 30 seconds or less and a total burning time of 250 seconds or less is classified as "V-1", and a maximum burning time of more than 30 seconds or a total burning time of more than 250 seconds is classified as "NG" as shown in Table 1. Shorter maximum and total burning times indicate better flame retardancy of the cured product.

[0064] [Table 1]

Claims

1. A liquid resin composition used for sealing a power module by casting, comprising a power module substrate on which a circuit layer is formed, and a power semiconductor element mounted on the circuit layer of the power module substrate, The liquid resin composition, epoxy resin, inorganic fillers, and Contains flame retardant, The flame retardant is a halogenated compound having a melting point of 250°C or higher and 600°C or lower. Liquid resin composition.

2. A liquid resin composition according to claim 1, The flame retardant is a halogenated compound having a 5% decomposition temperature of 300°C to 500°C, in a liquid resin composition.

3. A liquid resin composition according to claim 1, The flame retardant is a halogenated compound having a melting point of 300°C or more and 500°C or less, in a liquid resin composition.

4. A liquid resin composition according to claim 1, The flame retardant is a liquid resin composition which is a brominated compound.

5. A liquid resin composition according to claim 1, The flame retardant is a compound represented by formula (1) and a compound represented by formula (2): 【Chemistry 1】 【Chemistry 2】 A liquid resin composition comprising at least one selected from the following.

6. A liquid resin composition according to claim 1, The epoxy resin is a liquid resin composition containing an alicyclic epoxy resin.

7. The liquid resin composition according to claim 6, The epoxy resin further comprises a liquid bisphenol A type epoxy resin or a liquid bisphenol F type epoxy resin in the liquid resin composition.

8. A liquid resin composition according to claim 1, A liquid resin composition in which the flame retardancy of the cured product is V-0, as measured in accordance with the UL standard UL-94 vertical method (vertical combustion test).

9. A liquid resin composition according to claim 1, A two-component liquid resin composition.

10. A resin-encapsulated power module comprising: a power module substrate on which a circuit layer is formed; a power semiconductor element mounted on the circuit layer of the power module substrate; and a sealing material covering the power module substrate and the power semiconductor element, A resin-encapsulated power module wherein the encapsulating material consists of a cured product of the liquid resin composition described in any one of claims 1 to 9.

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