Sealing resin sheet

Abstract

To provide a resin sheet for sealing that is a sheet for sealing an electronic component chip mounted on a base material with a resin in a state of facing the base material through a cavity, which is suitable for achieving good hollow sealing property even when a ratio of a mounting height to a mounting interval of the electronic component chip is large, and provide an electronic component device.SOLUTION: A resin sheet X for sealing in the present invention has a sealing resin layer 11, and a sealing resin layer 12 in this order in a thickness direction D. The sealing resin layer 11 contains a first thermosetting resin and a first inorganic filler, and has an average linear thermal expansion ratio of 20 ppm / °C or less after curing. The sealing resin layer 12 contains a second thermosetting resin and a second inorganic filler, and has the average linear thermal expansion ratio of 20 ppm / °C or less after curing. A content ratio of the first inorganic filler in the sealing resin layer 11 is different from a content ratio of the second inorganic filler in the sealing resin layer 12. A ratio of thickness of the sealing resin layer 11 in the total thickness of the resin sheet X for sealing is 0.37 to 0.82.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an encapsulating resin sheet. [Background technology]

[0002] Conventionally, electronic component chips on a mounting substrate are sometimes encapsulated with an encapsulating resin sheet, which is a sheet-shaped encapsulating resin material containing a thermosetting resin.

[0003] On the other hand, there is known an electronic component chip that is mounted on a mounting substrate in a state in which the electronic component chip faces the mounting substrate with a gap therebetween. Such an electronic component chip is encapsulated in an encapsulating resin sheet, for example, as follows.

[0004] First, a sealing resin sheet of a predetermined thickness is pressed by a flat press against a plurality of electronic component chips (facing the substrate with a gap therebetween) bonded to the same surface of a mounting substrate and spaced apart from one another (pressing step). As a result, the sealing resin sheet is heated and softened, plastically deformed, and covers each electronic component chip. Next, the sealing resin sheet covering the electronic component chips is hardened by heating at a high temperature (hardening step). As a result, a hardened resin portion is formed around each electronic component chip on the substrate, and each electronic component chip is resin-sealed. After that, the hardened resin portion is cut together with the substrate by, for example, blade dicing, and each electronic component package is singulated (singulation step). Such a technology for resin sealing of electronic component chips is described, for example, in Patent Document 1 below. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-53470 A Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned encapsulating resin sheet is required to be fluidized in the heat-softened state in the above-mentioned pressing process, and the surface (exposed surface) opposite to the electronic component chip is required to be flattened (high fluidity requirement). In addition, the electronic component chip side of the encapsulating resin sheet is required to have the encapsulating resin softened by high-temperature heating not penetrate too much into the gap between the mounting substrate and the electronic component chip in the above-mentioned curing process (low fluidity requirement). Thus, the encapsulating resin sheet is required to have different characteristics regarding fluidity when heated and softened on the electronic component chip side and the opposite side. The encapsulating resin sheet described in Patent Document 1 has a laminated structure of a first resin layer (a resin layer arranged on the electronic component chip side when encapsulating the electronic component chip) and a second resin layer having different filler contents to meet these different requirements.

[0007] However, in the encapsulating resin sheet of Patent Document 1, the ratio of the thickness of the first resin layer to the thickness of the second resin layer is 0.05 to 0.3. That is, the ratio of the thickness of the first resin layer to the total thickness of the encapsulating resin sheet is 0.048 to 0.23. In the encapsulating resin sheet with such a thin first resin layer, the greater the ratio of the mounting height (the height of the electronic component chip from the substrate surface on the opposite side to the substrate) to the mounting interval (the distance between adjacent chips) of the electronic component chips on the substrate, the more likely the portion covering the chip corner (ridge) in the first resin layer on the electronic component chip side is to break in the above-mentioned encapsulating process. Specifically, the greater the mounting height of the electronic component chips on the substrate, the more likely the first resin layer is stretched and becomes thinner in the above-mentioned pressing process, and the more likely it is to break. In addition, the narrower the mounting interval of the electronic component chips on the substrate, the more likely it is the first resin layer is stretched and becomes thinner in the above-mentioned pressing process, and the more likely it is to break.

[0008] Furthermore, internal stress is generated in the encapsulating resin sheet (encapsulating resin material) that is heat-cured in the curing process. This internal stress may cause warping in the workpiece (e.g., a substrate on which multiple electronic component chips are encapsulated by the encapsulating resin sheet) obtained through the curing process. If the workpiece warps too much, the process after the curing process cannot be performed properly. For example, laser marking cannot be performed properly on the surface of the manufactured resin encapsulated body.

[0009] The present invention provides a sheet for resin-encapsulating electronic component chips mounted on a substrate in a state of facing the substrate with a gap therebetween, the sheet being suitable for achieving good hollow encapsulation even when the ratio of the mounting height to the mounting interval of the electronic component chips is large.The present invention also provides an electronic component device in which the electronic component chips are encapsulated with such a sealing resin sheet. [Means for solving the problem]

[0010] The present invention [1] relates to a sealing resin sheet having a first sealing resin layer and a second sealing resin layer in this order in a thickness direction, in which the first sealing resin layer contains a first thermosetting resin and a first inorganic filler, and has an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to a glass transition temperature after curing, and the second sealing resin layer contains a second thermosetting resin and a second inorganic filler, and has an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to a glass transition temperature after curing, a content ratio of the first inorganic filler in the first sealing resin layer and a content ratio of the second inorganic filler in the second sealing resin layer are different, and a ratio of a thickness of the first sealing resin layer to a total thickness of the sealing resin sheet is 0.37 or more and 0.82 or less.

[0011] The encapsulating resin sheet can be used to encapsulate electronic component chips mounted on a substrate in a state of facing the substrate with a gap therebetween, through the following pressing and curing steps. In the pressing step, the encapsulating resin sheet is pressed toward the substrate while being heated and softened in a state where the first encapsulating resin layer side of the encapsulating resin sheet is in contact with the electronic component chip on the substrate. In this step, the gap is closed along the side of the electronic component chip by the first encapsulating resin layer that is in close contact with the substrate around the electronic component chip. In the curing step, the encapsulating resin sheet covering the electronic component chip is further heated and cured. As a result, a cured resin portion is formed around the electronic component chip on the substrate, and the electronic component chip is resin-encapsulated. In the encapsulating resin sheet, the first inorganic filler content of the first encapsulating resin layer disposed on the electronic component chip side (first side) during such an encapsulation process is different from the second inorganic filler content of the second encapsulating resin layer disposed on the second side opposite to the first side. Such a configuration is suitable for making the first sealing resin layer and the second sealing resin layer exhibit different properties. Specifically, it is suitable for making the second sealing resin layer exhibit high fluidity so that the second side (exposed surface side) of the sealing resin sheet is flattened in the pressing process, and for making the first sealing resin layer exhibit low fluidity so that the sealing resin, which is once softened by high-temperature heating in the curing process, does not penetrate too much into the gap between the substrate and the electronic component chip.

[0012] In addition, in the encapsulating resin sheet, the ratio of the thickness of the first encapsulating resin layer to the total thickness of the encapsulating resin sheet is 0.37 or more as described above. This configuration is suitable for suppressing breakage of the portion of the first encapsulating resin layer covering the chip corner portion (ridge portion) in the press process, even when the ratio of the mounting height to the mounting interval of the electronic component chip is large. Such suppression of breakage of the first encapsulating resin layer is suitable for suppressing a part of the second encapsulating resin layer from flowing into the electronic component chip side through the broken portion of the first encapsulating resin layer. If the second encapsulating resin layer, which has a higher fluidity than the first encapsulating resin layer, flows in this way in the press process, the flowing resin flows between the electronic component chip and the first encapsulating resin layer, reaches the gap between the substrate and the electronic component chip, and further penetrates into the gap too far. The encapsulating resin sheet is suitable for avoiding such defects.

[0013] In addition, in the encapsulating resin sheet, the ratio of the thickness of the first encapsulating resin layer to the total thickness of the encapsulating resin sheet is 0.82 or less as described above. This configuration is suitable for ensuring the net fluidity of the encapsulating resin sheet in the pressing step and filling the gaps between adjacent chips with the encapsulating resin, even when the ratio of the mounting height to the mounting interval of the electronic component chips is large.

[0014] In addition, as described above, the first and second sealing resin layers of the encapsulating resin sheet have an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to the glass transition temperature after curing. Such a configuration is suitable for suppressing internal stress in the first and second sealing resin layers in the encapsulating resin sheet that have been cured through high-temperature heating and then cooled to room temperature, for example. The suppression of internal stress in the first and second sealing resin layers after curing is suitable for suppressing warpage in an electronic component device as a resin encapsulant manufactured using the encapsulating resin sheet. The suppression of warpage is suitable for suppressing detachment of the cured resin portion formed from the encapsulating resin sheet from the substrate.

[0015] The present invention [2] includes the encapsulating resin sheet according to the above [1], in which the first encapsulating resin layer has a thickness of 90 μm or more.

[0016] Such a configuration is preferable from the viewpoint of preventing the first sealing resin layer from breaking during the pressing step.

[0017] The present invention [3] includes the encapsulating resin sheet according to the above [1] or [2], wherein the first encapsulating resin layer has a minimum melt viscosity of 120 kPa·s or more.

[0018] Such a configuration is preferable for preventing the first sealing resin layer, which is once softened by high-temperature heating in the curing step, from penetrating too far (excessive penetration) into the gap between the base material and the electronic component chip.

[0019] The present invention [4] includes the encapsulating resin sheet according to any one of the above [1] to [3], wherein the first encapsulating resin layer has a minimum melt viscosity of 260 kPa·s or less.

[0020] Such a configuration is preferable for ensuring the net flowability of the sealing resin sheet in the pressing step and for filling the gaps between adjacent chips with the sealing resin.

[0021] The present invention [5] includes the sealing resin sheet according to any one of the above [1] to [4], further comprising a third sealing resin layer between the first sealing resin layer and the second sealing resin layer, the third sealing resin layer including a third thermosetting resin and a third inorganic filler, and having an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to a glass transition temperature after curing.

[0022] It is preferable that the encapsulating resin sheet includes the above-mentioned third encapsulating resin layer in addition to the first encapsulating resin layer in order to prevent the second encapsulating resin layer from flowing toward the electronic component chip in the pressing step.

[0023] The present invention [6] includes the sealing resin sheet according to any one of the above [1] to [5], wherein the third sealing resin layer is in direct contact with the first sealing resin layer, and a ratio of a total thickness of the first sealing resin layer and a thickness of the third sealing resin layer to a total thickness of the sealing resin sheet is 0.4 or more and 0.82 or less.

[0024] Such a configuration is preferable for preventing the second sealing resin layer from flowing toward the electronic component chip during the pressing process.

[0025] The present invention [7] includes the encapsulating resin sheet according to any one of the above [1] to [6], wherein the content of the inorganic filler in each encapsulating resin layer is 75 mass % or more.

[0026] Such a configuration is preferable for achieving the above-mentioned average linear thermal expansion coefficient of 20 ppm / ° C. or less in each sealing resin layer.

[0027] The present invention [8] includes the encapsulating resin sheet according to any one of the above [1] to [7], wherein the content of the inorganic filler in each encapsulating resin layer is 90 mass % or less.

[0028] Such a configuration is preferable for ensuring the flowability required for the sealing resin sheet in the pressing step.

[0029] The present invention [9] includes an electronic component device comprising a substrate, an electronic component chip mounted on the substrate in a state facing the substrate with a gap therebetween, and a cured resin portion formed from the sealing resin sheet described in any one of [1] to [8] above, and sealing the electronic component chip and the gap.

[0030] In this electronic component device, the electronic component chip is sealed with the cured resin portion formed from the above-mentioned sealing resin sheet, so that it is suitable for realizing good hollow sealing properties. [Brief description of the drawings]

[0031] [Figure 1] 1 is a schematic cross-sectional view of an embodiment of an encapsulating resin sheet of the present invention. FIG. [Diagram 2] This shows a method for encapsulating electronic component chips on a substrate using the encapsulating resin sheet shown in Fig. 1. Fig. 2A shows a process of placing a workpiece and an encapsulating resin sheet between press plates of a flat plate press, Fig. 2B shows a pressing process, and Fig. 2C shows a curing process. [Diagram 3] 2 is a schematic cross-sectional view of a modified example of the encapsulating resin sheet shown in Fig. 1. In this modified example, the encapsulating resin sheet has a three-layer structure. [Figure 4] 4A shows a step of preparing an encapsulating resin sheet, FIG. 4B shows a step of placing a work and an encapsulating resin sheet between press plates of a flat plate press, FIG. 4C shows a pressing step, and FIG. 4D shows a curing step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] An encapsulating resin sheet X as one embodiment of the encapsulating resin sheet of the present invention is a sheet-like encapsulating resin material for encapsulating electronic component chips such as semiconductor chips, and includes an encapsulating resin layer 11 and an encapsulating resin layer 12 in this order in a thickness direction D, as shown in Fig. 1. In addition, the encapsulating resin sheet X extends in a direction perpendicular to the thickness direction D.

[0033] The encapsulating resin layer 11 is a layer formed from a first thermosetting composition. The first thermosetting composition includes a first thermosetting resin and a first inorganic filler. That is, the encapsulating resin layer 11 includes a first thermosetting resin and a first inorganic filler. The encapsulating resin layer 11 is in a semi-cured state (B-stage state).

[0034] Examples of the first thermosetting resin include epoxy resin, silicone resin, urethane resin, polyimide resin, urea resin, melamine resin, and unsaturated polyester resin. These first thermosetting resins may be used alone or in combination of two or more. The content of the first thermosetting resin in the first thermosetting composition is preferably 3% by mass or more, more preferably 3.5% by mass or more. The content of the first thermosetting resin in the first thermosetting composition is preferably 30% by mass or less, more preferably 25% by mass or less.

[0035] The first thermosetting resin preferably contains an epoxy resin. Examples of the epoxy resin include bifunctional epoxy resins and trifunctional or higher polyfunctional epoxy resins. Examples of the bifunctional epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, modified bisphenol A type epoxy resins, modified bisphenol F type epoxy resins, and biphenyl type epoxy resins. Examples of the trifunctional or higher polyfunctional epoxy resins include phenol novolac type epoxy resins, cresol novolac type epoxy resins, trishydroxyphenylmethane type epoxy resins, tetraphenylolethane type epoxy resins, and dicyclopentadiene type epoxy resins. These epoxy resins may be used alone or in combination of two or more. As the epoxy resin, a bifunctional epoxy resin is preferably used, and more preferably, a bisphenol F type epoxy and / or a bisphenol A type epoxy resin is used.

[0036] The epoxy equivalent of the epoxy resin is preferably 10 g / eq or more, more preferably 50 g / eq or more, and even more preferably 100 g / eq or more. The epoxy equivalent of the epoxy resin is preferably 650 g / eq or less, more preferably 600 g / eq or less, and even more preferably 550 g / eq or less. When the first thermosetting resin contains a plurality of epoxy resins, the weighted average epoxy equivalent of the plurality of epoxy resins is preferably 10 g / eq or more, more preferably 50 g / eq or more, and even more preferably 100 g / eq or more. The weighted average epoxy equivalent is preferably 650 g / eq or less, more preferably 600 g / eq or less, and even more preferably 550 g / eq or less.

[0037] When an epoxy resin is used, the first thermosetting resin preferably contains a phenolic resin as a curing agent for the epoxy resin. Such a configuration is suitable for the encapsulating resin sheet X to exhibit high heat resistance and high chemical resistance after curing, and is therefore suitable for forming an encapsulating material with excellent encapsulation reliability. As the phenolic resin, preferably, a novolac type phenolic resin and a triphenylmethane type phenolic resin are mentioned. As the novolac type phenolic resin, for example, a phenol novolac resin, a phenol aralkyl resin, a trishydroxyphenylmethane novolac resin, a cresol novolac resin, a tert-butylphenol novolac resin, and a nonylphenol novolac resin are mentioned. These phenolic resins may be used alone or in combination of two or more kinds.

[0038] In the first thermosetting composition, the amount of hydroxyl groups in the phenolic resin as a curing agent relative to 1 equivalent of the epoxy group of the epoxy resin is preferably 0.7 equivalents or more, more preferably 0.9 equivalents or more. In the first thermosetting composition, the amount of hydroxyl groups in the phenolic resin as a curing agent relative to 1 equivalent of the epoxy group of the epoxy resin is preferably 1.5 equivalents or less, more preferably 1.2 equivalents or less. In addition, the amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin is preferably 20 parts by mass or more, more preferably 40 parts by mass or more. The amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin is preferably 80 parts by mass or less, more preferably 60 parts by mass or less.

[0039] The first thermosetting composition preferably contains a curing accelerator. The curing accelerator is a catalyst (thermosetting catalyst) that accelerates the curing of a thermosetting resin by heating. Examples of the curing accelerator include an imidazole compound and an organic phosphorus compound. Examples of the imidazole compound include 2-phenyl-4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Examples of the organic phosphorus compound include triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine. As the curing accelerator, an imidazole compound is preferably used, and more preferably 2-phenyl-4,5-dihydroxymethylimidazole is used. The amount of the curing accelerator to be blended relative to 100 parts by mass of the first thermosetting resin is, for example, 0.05 parts by mass or more, and, for example, 5 parts by mass or less.

[0040] Examples of the first inorganic filler include a layered silicate compound and an inorganic filler other than the layered silicate compound. The first inorganic filler preferably includes a layered silicate compound and an inorganic filler other than the layered silicate compound.

[0041] The layered silicate compound is a component that thickens the first thermosetting composition while imparting thixotropy to the first thermosetting composition, and is dispersed in the first thermosetting composition. Examples of the layered silicate compound include smectite, kaolinite, halloysite, talc, and mica. Examples of the smectite include montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. As the layered silicate compound, smectite is preferably used because it is easily mixed with the thermosetting resin, and more preferably montmorillonite is used.

[0042] The layered silicate compound may be an unmodified one whose surface is not modified, or may be a modified one whose surface is modified with an organic component. For example, from the viewpoint of affinity with the first thermosetting resin, preferably, a layered silicate compound whose surface is modified with an organic component is used, more preferably, an organically modified smectite whose surface is modified with an organic component is used, and even more preferably, an organically modified bentonite whose surface is modified with an organic component is used.

[0043] Examples of organic components include organic cations (onium ions) such as ammonium, imidazolium, pyridinium, and phosphonium. Examples of ammonium include dimethyl distearyl ammonium, distearyl ammonium, octadecyl ammonium, hexyl ammonium, octyl ammonium, 2-hexyl ammonium, dodecyl ammonium, and trioctyl ammonium. Examples of imidazolium include methyl stearyl imidazolium, distearyl imidazolium, methyl hexyl imidazolium, dihexyl imidazolium, methyl octylimidazolium, dioctylimidazolium, methyl dodecyl imidazolium, and didodecyl imidazolium. Examples of pyridinium include stearyl pyridinium, hexyl pyridinium, octyl pyridinium, and dodecyl pyridinium. Examples of the phosphonium include dimethyl distearyl phosphonium, distearyl phosphonium, octadecyl phosphonium, hexyl phosphonium, octyl phosphonium, 2-hexyl phosphonium, dodecyl phosphonium, and trioctyl phosphonium. The organic cation may be used alone or in combination of two or more. As the organic cation, ammonium is preferably used, and dimethyl distearyl ammonium is more preferably used.

[0044] As the organically modified layered silicate compound, preferably, organically modified smectite whose surface is modified with ammonium is used, and more preferably, organically modified bentonite whose surface is modified with dimethyldistearylammonium is used.

[0045] The average particle size of the layered silicate compound is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. The average particle size of the layered silicate compound is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. The average particle size of the layered silicate compound is the median size in the volumetric particle size distribution (the particle size at which the volume cumulative frequency reaches 50% from the small diameter side), and can be determined, for example, based on the particle size distribution obtained by a laser diffraction / scattering method (the same applies to the average particle sizes of other inorganic fillers).

[0046] As the layered silicate compound, commercially available products can be used. Commercially available organic bentonite products include, for example, the Esben series (manufactured by Hojun Co., Ltd.).

[0047] The content of the layered silicate compound in the first thermosetting composition (i.e., the content of the layered silicate compound in the encapsulating resin layer 11) is preferably 1 mass% or more, more preferably 1.2 mass% or more, and even more preferably 1.4 mass% or more. Such a configuration is suitable for increasing the viscosity of the encapsulating resin layer 11 while allowing the encapsulating resin layer 11 to exhibit thixotropic properties in which the viscosity is lower when the encapsulating resin layer 11 is subjected to a pressing force than when it is not subjected to the pressing force. From the viewpoint of avoiding excessive increase in the viscosity of the first thermosetting composition, the content of the layered silicate compound in the first thermosetting composition is preferably 6 mass% or less, more preferably 5 mass% or less, and even more preferably 4 mass% or less.

[0048] Examples of inorganic fillers other than layered silicate compounds include silicon compounds such as silica and silicon nitride (silicon compounds other than layered silicate compounds), and silicate compounds other than layered silicate compounds such as orthosilicate, sorosilicate, and inosilicate. Examples of inorganic fillers other than layered silicate compounds include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, and boron nitride. These inorganic fillers may be used alone or in combination of two or more. As the inorganic filler, preferably, a silicon compound other than layered silicate compounds is used, and more preferably, silica is used.

[0049] Examples of the shape of the inorganic filler other than the layered silicate compound include a substantially spherical shape, a substantially plate-like shape, a substantially needle-like shape, and an irregular shape, with a substantially spherical shape being preferred.

[0050] The average particle size of the inorganic filler other than the layered silicate compound (when the inorganic filler has a shape other than a substantially spherical shape, the average maximum length of the inorganic filler) is preferably 0.1 μm or more, more preferably 0.5 μm or more, and is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less.

[0051] The surface of the inorganic filler other than the layered silicate compound may be partially or entirely treated with a surface treatment agent such as a silane coupling agent.

[0052] The content of the inorganic filler other than the layered silicate compound in the first thermosetting composition is preferably 73 mass% or more, more preferably 76 mass% or more, and even more preferably 78 mass% or more. Such a configuration is suitable for suppressing expansion and contraction due to temperature changes in the sealing resin layer 11. The content is preferably 90 mass% or less, more preferably 85 mass% or less, and even more preferably 83 mass% or less. Such a configuration is suitable for avoiding excessive thickening of the first thermosetting composition and ensuring the fluidity of the sealing resin layer 11 in the pressing step described below.

[0053] The content ratio R1 of the first inorganic filler in the first thermosetting composition (encapsulating resin layer 11) is preferably 75 mass% or more, more preferably 78 mass% or more, and even more preferably 80 mass% or more. Such a configuration is suitable for suppressing expansion and contraction due to temperature change in the encapsulating resin layer 11, and is preferable for achieving an average linear thermal expansion coefficient of 20 ppm / °C or less. The content ratio R1 is preferably 90 mass% or less, more preferably 87 mass% or less, and even more preferably 85 mass% or less. Such a configuration is suitable for avoiding excessive thickening of the first thermosetting composition and ensuring the fluidity of the encapsulating resin layer 11 in the pressing step described below.

[0054] The ratio of the layered silicate compound in the first inorganic filler is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more. The ratio is preferably 8 mass% or less, more preferably 7 mass% or less, and even more preferably 6.5 mass% or less. These configurations are suitable for realizing a good balance between suppressing expansion and contraction due to temperature changes in the sealing resin layer 11, ensuring fluidity in the pressing process described below, and expressing the above-mentioned thixotropy.

[0055] The first thermosetting composition may contain other components, such as a thermoplastic resin, a pigment, and a silane coupling agent.

[0056] Examples of thermoplastic resins include acrylic resins, natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polybutadiene resins, polycarbonate resins, thermoplastic polyimide resins, polyamide resins, phenoxy resins, saturated polyester resins (PET, etc.), polyamideimide resins, fluororesins, and styrene-isobutylene-styrene block copolymers. These thermoplastic resins may be used alone or in combination of two or more.

[0057] As the thermoplastic resin, from the viewpoint of ensuring compatibility between the thermosetting resin and the thermoplastic resin, an acrylic resin is preferably used.

[0058] Examples of acrylic resins include (meth)acrylic polymers, which are polymers of monomer components including (meth)acrylic acid alkyl esters having a linear or branched alkyl group and other monomers (copolymerizable monomers).

[0059] Examples of the alkyl group of the (meth)acrylic acid alkyl ester include alkyl groups having a carbon number of 1 to 6. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, a pentyl group, and a hexyl group.

[0060] Examples of the copolymerizable monomer include carboxyl group-containing monomers, acid anhydride monomers, glycidyl group-containing monomers, hydroxyl group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, and acrylonitrile. Examples of the carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomers include maleic anhydride and itaconic anhydride. Examples of the glycidyl group-containing monomers include glycidyl acrylate and glycidyl methacrylate. Examples of the hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. Examples of sulfonic acid group-containing monomers include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl(meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid. Examples of phosphoric acid group-containing monomers include 2-hydroxyethylacryloylphosphate. These copolymerizable monomers may be used alone or in combination of two or more.

[0061] The glass transition temperature (Tg) of the thermoplastic resin is preferably −70° C. or higher. The glass transition temperature is preferably 0° C. or lower, more preferably −5° C. or lower.

[0062] The glass transition temperature (Tg) of a polymer can be determined by the following Fox formula (theoretical value). The Fox formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of a monomer constituting the polymer. In the following Fox formula, Tg represents the glass transition temperature (°C) of a polymer, Wi represents the weight fraction of a monomer i constituting the polymer, and Tgi represents the glass transition temperature (°C) of a homopolymer formed from the monomer i. The glass transition temperature of a homopolymer can be determined by literature values. For example, the glass transition temperatures of various homopolymers are listed in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7: Introduction to Synthetic Resins for Paints" (Kyozo Kitaoka, Polymer Publishing Association, 1995). On the other hand, the glass transition temperature of a homopolymer of a monomer can also be determined by a method specifically described in JP-A-2007-51271.

[0063] Fox formula 1 / (273+Tg)=Σ[Wi / (273+Tgi)]

[0064] The weight average molecular weight of the thermoplastic resin is preferably 100,000 or more, and more preferably 300,000 or more. The weight average molecular weight of the thermoplastic resin is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The weight average molecular weight of the resin is measured by gel permeation chromatography (GPC) based on a standard polystyrene equivalent value.

[0065] The content of the thermoplastic resin in the first thermosetting composition is preferably 1% by mass or more, more preferably 2% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less.

[0066] Examples of the pigment include black pigments such as carbon black. The particle size of the pigment is, for example, 0.001 μm or more, and, for example, 1 μm or less. The particle size of the pigment is an arithmetic mean diameter obtained by observing the pigment with an electron microscope. The content of the pigment in the first thermosetting composition is, for example, 0.1 mass % or more, and, for example, 2 mass % or less.

[0067] Examples of the silane coupling agent include silane coupling agents containing an epoxy group. Examples of the silane coupling agent containing an epoxy group include 3-glycidoxydialkyldialkoxysilane and 3-glycidoxyalkyltrialkoxysilane. Examples of the 3-glycidoxydialkyldialkoxysilane include 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. Examples of the 3-glycidoxyalkyltrialkoxysilane include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. As the silane coupling agent, preferably, 3-glycidoxyalkyltrialkoxysilane is used, more preferably, 3-glycidoxypropyltrimethoxysilane is used. The content of the silane coupling agent in the first thermosetting composition is preferably 0.1% by mass or more, more preferably 1% by mass or more. The content is preferably 10% by mass or less, more preferably 5% by mass or less.

[0068] The sealing resin layer 12 is a layer formed from a second thermosetting composition. The second thermosetting composition includes a second thermosetting resin and a second inorganic filler. That is, the sealing resin layer 12 includes a second thermosetting resin and a second inorganic filler. The sealing resin layer 12 is in a semi-cured state (B-stage state).

[0069] The second thermosetting resin may be, for example, the first thermosetting resin described above. The content of the second thermosetting resin in the second thermosetting composition is preferably 3% by mass or more, more preferably 3.5% by mass or more. The content of the second thermosetting resin in the second thermosetting composition is preferably 30% by mass or less, more preferably 25% by mass or less.

[0070] The second thermosetting resin preferably contains an epoxy resin. Examples of the epoxy resin include the epoxy resins described above for the first thermosetting composition, and preferably a bifunctional epoxy resin is used, more preferably a bisphenol A type epoxy resin and / or a bisphenol F type epoxy resin. The preferred range of the epoxy equivalent of the epoxy resin in the second thermosetting composition is the same as the preferred range of the epoxy equivalent of the epoxy resin in the first thermosetting composition described above.

[0071] When an epoxy resin is used as the second thermosetting resin, the second thermosetting resin preferably contains a phenolic resin as a curing agent for the epoxy resin. The phenolic resin preferably includes a novolac type phenolic resin and a triphenylmethane type phenolic resin. In the second thermosetting composition, the amount of hydroxyl groups in the phenolic resin as a curing agent relative to one equivalent of the epoxy group of the epoxy resin is the same as the amount of hydroxyl groups in the phenolic resin as a curing agent relative to one equivalent of the epoxy group of the epoxy resin described above for the first thermosetting composition. In addition, the amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin in the second thermosetting composition is the same as the amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin described above for the first thermosetting composition.

[0072] The second thermosetting composition preferably contains a curing accelerator. Examples of the curing accelerator include the curing accelerators described above for the first thermosetting composition. The amount of the curing accelerator to be blended relative to 100 parts by mass of the second thermosetting resin is, for example, 0.05 parts by mass or more and, for example, 5 parts by mass or less.

[0073] The second inorganic filler may be, for example, the first inorganic filler described above in relation to the first thermosetting composition. As the second inorganic filler, preferably, an inorganic filler other than a layered silicate compound is used, more preferably, a silicon compound other than a layered silicate compound is used, and even more preferably, silica is used.

[0074] The shape of the second inorganic filler may be, for example, substantially spherical, substantially plate-like, substantially needle-like, or irregular, with a substantially spherical shape being preferred. The average particle diameter of the second inorganic filler (when the second inorganic filler has a shape other than substantially spherical, the average value of the maximum length of the second inorganic filler) is preferably 0.1 μm or more, more preferably 0.5 μm or more. The average particle diameter is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. The surface of the second inorganic filler may be partially or entirely treated with a surface treatment agent such as a silane coupling agent.

[0075] The content ratio R2 of the second inorganic filler in the second thermosetting composition (encapsulating resin layer 12) is different from the content ratio R1 of the first inorganic filler in the encapsulating resin layer 11. The content ratio R2 is, for example, higher than the content ratio R1, and for example, lower than the content ratio R1.

[0076] The content ratio R2 of the second inorganic filler in the second thermosetting composition is preferably 75 mass% or more, more preferably 78 mass% or more, and even more preferably 80 mass% or more, as long as it is different from the content ratio R1. Such a configuration is suitable for suppressing expansion and contraction due to temperature change in the encapsulating resin layer 12, and is preferable for achieving an average linear thermal expansion coefficient of 20 ppm / °C or less. As long as it is different from the content ratio R1, the content ratio R2 is preferably 90 mass% or less, more preferably 87 mass% or less, and even more preferably 85 mass% or less. Such a configuration is suitable for ensuring the fluidity of the encapsulating resin layer 12 in the pressing process described below.

[0077] The second thermosetting composition may contain other components, such as thermoplastic resins, pigments, and silane coupling agents, as described above for the first thermosetting composition.

[0078] The encapsulating resin sheet X can be produced, for example, by forming the encapsulating resin layer 11 and the encapsulating resin layer 12, respectively, and then laminating the encapsulating resin layer 11 and the encapsulating resin layer 12 together.

[0079] The encapsulating resin layer 11 can be formed, for example, as follows. First, the components described above for the first thermosetting composition are mixed with a solvent in a predetermined ratio to prepare a varnish of the first thermosetting composition. Examples of the solvent include methyl ethyl ketone, ethyl acetate, and toluene. Next, the varnish is applied onto a substrate such as a release sheet to form a coating film, and the coating film is then dried by heating. This allows the encapsulating resin layer 11 to be formed in a sheet shape and in a semi-cured state.

[0080] The encapsulating resin layer 12 can be formed, for example, as follows. First, the components described above for the second thermosetting composition are mixed with a solvent in a predetermined ratio to prepare a varnish of the second thermosetting composition. Next, the varnish is applied onto a substrate such as a release sheet to form a coating film, and the coating film is then dried by heating. This allows the encapsulating resin layer 12 to be formed in a sheet shape and in a semi-cured state.

[0081] The encapsulating resin sheet X may be produced by forming an encapsulating resin layer 11 on a substrate, and then forming an encapsulating resin layer 12 on the encapsulating resin layer 11. Alternatively, the encapsulating resin sheet X may be produced by forming an encapsulating resin layer 12 on a substrate, and then forming an encapsulating resin layer 11 on the encapsulating resin layer 12.

[0082] The ratio of the thickness H1 of the encapsulating resin layer 11 to the total thickness of the encapsulating resin sheet X is 0.37 or more, preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. That is, the ratio of the thickness H2 of the encapsulating resin layer 12 to the total thickness of the encapsulating resin sheet X is 0.4 or less, preferably 0.5 or less, more preferably 0.6 or less, and even more preferably 0.63 or less. Such a configuration is suitable for suppressing breakage of the encapsulating resin layer 11 in the pressing process described later.

[0083] The ratio of the thickness H1 of the encapsulating resin layer 11 to the total thickness of the encapsulating resin sheet X is 0.82 or less, and preferably 0.8 or less. That is, the ratio of the thickness H2 of the encapsulating resin layer 12 to the total thickness of the encapsulating resin sheet X is 0.2 or more, and preferably 0.18 or more. Such a configuration is suitable for ensuring the net fluidity of the encapsulating resin sheet X in the pressing process described later, and filling the gaps between adjacent chips with the encapsulating resin.

[0084] The thickness of the encapsulating resin layer 11 is preferably 90 μm or more, more preferably 100 μm or more, and even more preferably 120 μm or more. Such a configuration is preferable from the viewpoint of suppressing breakage of the encapsulating resin layer 11 in the pressing step described later. The thickness of the encapsulating resin layer 11 is, for example, 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 180 μm or less. Such a configuration is preferable for ensuring the net fluidity of the encapsulating resin sheet X in the pressing step described later and filling the gaps between adjacent chips with the encapsulating resin.

[0085] The thickness H2 of the encapsulating resin layer 12 is preferably 30 μm or more, more preferably 50 μm or more, further preferably 80 μm or more, and particularly preferably 100 μm or more. The thickness H2 of the encapsulating resin layer 12 is, for example, 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, and particularly preferably 180 μm or less.

[0086] The total thickness of the encapsulating resin sheet X is preferably 150 μm or more, more preferably 200 μm or more, and even more preferably 230 μm or more. The total thickness of the encapsulating resin sheet X is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and particularly preferably 280 μm or less.

[0087] The minimum melt viscosity of the encapsulating resin layer 11 is preferably 120 kPa·s or more, more preferably 150 kPa·s or more, even more preferably 180 kPa·s or more, and particularly preferably 200 kPa·s or more. Such a configuration is preferable for preventing the encapsulating resin layer 11, which is once softened by high-temperature heating in the curing step described later, from penetrating too far into the gap between the substrate and the electronic component chip (over-penetration). The minimum melt viscosity of the encapsulating resin layer can be obtained by measuring the viscoelasticity of the encapsulating resin layer. The viscoelasticity measurement can be performed using a rheometer. As the rheometer, for example, "HAAKE MARS III" manufactured by Thermo Fisher Scientific can be used. In the measurement, the frequency is 1 Hz, the strain value is 0.005%, the temperature range is 50°C to 90°C, and the heating rate is 30°C / min. Specifically, the minimum melt viscosity can be obtained by the measurement method described later in the examples.

[0088] The minimum melt viscosity of the encapsulating resin layer 11 is preferably 260 kPa s or less, more preferably 250 kPa s or less, and further preferably 240 kPa s or less. Such a configuration is preferable for ensuring the net fluidity of the encapsulating resin sheet X in the pressing step described later, and for filling the gaps between adjacent chips with the encapsulating resin.

[0089] The minimum melt viscosity of the encapsulating resin layer 12 is preferably 1 kPa·s or more, more preferably 3 kPa·s or more, and is preferably 200 kPa·s or less, more preferably 180 kPa·s or less. Such a configuration is preferable for ensuring the net fluidity of the encapsulating resin sheet X in the pressing step described later, and for filling the gaps between adjacent chips with the encapsulating resin.

[0090] The sealing resin layer 11 has an average linear thermal expansion coefficient Z1 of 20 ppm / °C or less in the temperature range from -40°C to the glass transition temperature after being cured by heating at 150°C for 1 hour, and the sealing resin layer 12 has an average linear thermal expansion coefficient Z2 of 20 ppm / °C or less in the temperature range from -40°C to the glass transition temperature after being cured by heating at 150°C for 1 hour. Such a configuration is suitable for suppressing internal stress in the sealing resin layers 11 and 12 in the sealing resin sheet X that have been cured through high-temperature heating and then cooled to room temperature, for example. The average linear thermal expansion coefficient Z1 is preferably 18 ppm / °C or less, more preferably 17 ppm / °C or less. The average linear thermal expansion coefficient Z2 is preferably 18 ppm / °C or less, more preferably 17 ppm / °C or less. The average linear thermal expansion coefficient of the sealing resin layer can be measured using a thermomechanical analyzer (TMA). An example of the TMA is "Q400 TMA" manufactured by TA Instruments Japan. In the measurement, the mode is tensile mode, the heating rate is 1°C / min, the modulation conditions are ±5.000°C / 300 seconds, and the measurement temperature range is -40°C to 260°C. Specifically, the average linear thermal expansion coefficient can be obtained by the measurement method described later in the examples.

[0091] The ratio of the average linear thermal expansion coefficient Z2 to the average linear thermal expansion coefficient Z1 is preferably 0.7 or more, more preferably 0.8 or more, even more preferably 0.9 or more, and is preferably 1.3 or less, more preferably 1.2 or less, even more preferably 1.1 or less. Such a configuration is preferable for suppressing warpage of the sealing resin sheet X after curing.

[0092] FIG. 2 shows a method for sealing an electronic component chip on a substrate using a sealing resin sheet X.

[0093] Next, as shown in FIG. 2A, the workpiece W and the sealing resin sheet X are placed between a first press plate P1 and a second press plate P2 of a flat plate press (placement step).

[0094] The workpiece W includes a substrate S and a plurality of chips 21. The substrate S is a base material that is later divided into single mounting substrates, and has a mounting surface Sa. The mounting surface Sa is provided with a terminal for mounting (not shown). The chip 21 is an electronic component chip such as a semiconductor chip, and has a main surface 21a and a side surface 21b. The main surface 21a is provided with a terminal for external connection (not shown). The chip 21 is mounted on the substrate S via bump electrodes 22 in a state facing the substrate S across a gap G. Each bump electrode 22 is interposed between a terminal provided on the mounting surface Sa of the substrate S and a terminal provided on the main surface 21a of the chip 21, and electrically connects the substrate S and the chip 21.

[0095] The mounting height of the chip 21 on the substrate S (the height from the surface of the substrate S on the side of the chip 21 opposite the substrate S) is, for example, 200 μm or more, preferably 220 μm or more, and more preferably 250 μm or more. The mounting height is, for example, 400 μm or less, preferably 350 μm or less, and more preferably 300 μm or less.

[0096] The distance between the substrate S and the chip 21 is, for example, 10 μm or more, preferably 15 μm or more, and more preferably 20 μm or more. The distance is, for example, 80 μm or less, preferably 60 mm or less, and more preferably 50 μm or less.

[0097] The multiple chips 21 are mounted on the mounting surface Sa of the substrate S at intervals in the planar direction. The interval (mounting interval) between adjacent chips 21 is, for example, 50 μm or more, preferably 100 μm or more, and more preferably 200 μm or more. The interval between adjacent chips 21 is, for example, 10 mm or less, preferably 5 mm or less, and more preferably 1 mm or less.

[0098] In this step, the work W is placed on the first press plate P1 so that the substrate S of the work W contacts the first press plate P1. The encapsulating resin sheet X is laminated on the work W so that the encapsulating resin layer 11 contacts the chip 21 of the work W.

[0099] 2B, the encapsulating resin sheet X and the workpiece W are pressed in the thickness direction D by a first press plate P1 and a second press plate P2 (pressing step). Specifically, in a state where the encapsulating resin layer 11 side of the encapsulating resin sheet X contacts the chip 21 on the substrate S, the encapsulating resin sheet X is pressed toward the substrate S while being heated and softened.

[0100] The pressing pressure is, for example, 0.01 MPa or more, and preferably 0.05 MPa or more. The pressing pressure is, for example, 10 MPa or less, and preferably 5 MPa or less. The pressing time is, for example, 0.3 minutes or more, and preferably 0.5 minutes or less. The pressing time is, for example, 10 minutes or more, and preferably 5 minutes or less. The heating temperature during pressing is, for example, 40°C or more, and preferably 60°C or more. The heating temperature is, for example, 100°C or less, and preferably 95°C or less.

[0101] In this process, the sealing resin sheet X, while maintaining the B stage, deforms in accordance with the outer shape of the chips 21, covers the side surfaces 21b of each chip 21, and comes into contact with the mounting surface Sa of the substrate S that does not overlap with the chips 21 in a plan view. The sealing resin layer 11 that is in close contact with the substrate S around the chips 21 closes the gaps G along the side surfaces 21b of the chips 21 (the open edges of the gaps G are closed).

[0102] The deformed sealing resin sheet X is allowed to slightly penetrate into the gap G between the substrate S and the chip 21. Specifically, the sealing resin sheet X is allowed to have a penetration length L1 into the gap G based on the side surface 21b of the chip 21.

[0103] The penetration length L1 is preferably 50 μm or less, more preferably 30 μm or less. Such a configuration is suitable for securing an area on the main surface 21a of the chip 21 where wiring can be formed, and is also suitable for securing an area on the mounting surface Sa of the substrate S where wiring can be formed, and therefore is useful for improving the functionality of the resin encapsulation body. Moreover, the penetration length L1 is preferably 0 μm or more. Such a configuration is suitable for appropriately sealing the chip 21 and the gap G so that the gap G does not open to the outside of the resin encapsulation body in an electronic component device as a resin encapsulation body after singulation, which will be described later.

[0104] Next, the workpiece W sealed with the sealing resin sheet X is removed from the flat plate press, and then the sealing resin sheet X is heated and cured (curing step) as shown in Fig. 2C. As a result, a cured resin portion is formed around each chip 21 on the substrate S, and each chip 21 is sealed with resin.

[0105] The heating temperature (cure temperature) is, for example, 100° C. or higher, preferably 120° C. or higher. The heating temperature (cure temperature) is, for example, 200° C. or lower, preferably 180° C. or lower. The heating time is, for example, 10 minutes or longer, preferably 30 minutes or longer. The heating time is, for example, 180 minutes or shorter, preferably 120 minutes or shorter.

[0106] The penetration length L2 of the cured sealing resin sheet X into the gap G is preferably 50 μm or less, more preferably 30 μm or less. Such a configuration is suitable for securing an area on the main surface 21a of the chip 21 where wiring can be formed, and is also suitable for securing an area on the mounting surface Sa of the substrate S where wiring can be formed, and therefore is useful for improving the functionality of the resin sealing body. The penetration length L2 is preferably 0 μm or more. Such a configuration is suitable for appropriately sealing the chip 21 and the gap G so that the gap G does not open to the outside of the resin sealing body in an electronic component device as a resin sealing body after individualization described below.

[0107] Thereafter, the cured sealing resin sheet X and the substrate S are cut along a predetermined cutting line, for example, by blade dicing, and are singulated into electronic component devices as resin encapsulated bodies (singulation process). The electronic component device thus obtained includes the substrate S as a base material, a chip 21 as an electronic component chip mounted on the substrate S in a state facing the substrate S with a gap G therebetween, and a cured resin portion formed from the sealing resin sheet X and sealing the chip 21 and the gap G.

[0108] In the encapsulating resin sheet X, the content ratio R1 of the first inorganic filler in the encapsulating resin layer 11 arranged on the chip 21 side (first side) in the above-mentioned encapsulating process is different from the content ratio R2 of the second inorganic filler in the encapsulating resin layer 12 arranged on the second side opposite to the first side. Such a configuration is suitable for making the encapsulating resin layer 11 and the encapsulating resin layer 12 exhibit different characteristics. Specifically, in the pressing process (FIG. 2B), high fluidity is exhibited in the encapsulating resin layer 12 so that the flattening of the second side (exposed surface side) of the encapsulating resin sheet X progresses, while low fluidity is exhibited in the encapsulating resin layer 11 so that the encapsulating resin, which is once softened by high-temperature heating in the curing process (FIG. 2C), does not penetrate too much into the gap G between the substrate S and the chip 21.

[0109] In addition, in the encapsulating resin sheet X, the ratio of the thickness of the encapsulating resin layer 11 to the total thickness of the sheet is 0.37 or more, preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more, as described above. This configuration is suitable for suppressing breakage of the portion of the encapsulating resin layer 11 covering the corners (ridges) of the chip 21 in the pressing process (FIG. 2B), even when the ratio of the mounting height to the mounting interval of the chip 21 is large. Such suppression of breakage of the encapsulating resin layer 11 is suitable for suppressing a part of the encapsulating resin layer 12 from flowing into the chip 21 side through the broken portion of the encapsulating resin layer 11. If the flow occurs in the encapsulating resin layer 12, which has a higher fluidity than the encapsulating resin layer 11, in the pressing process, the flowing resin may flow between the chip 21 and the encapsulating resin layer 11, reach the gap G between the substrate S and the chip 21, and even enter the gap G too far. The encapsulating resin sheet X is suitable for avoiding such a defect.

[0110] In addition, the ratio of the thickness H1 of the encapsulating resin layer 11 to the total thickness of the encapsulating resin sheet X is 0.82 or less, and preferably 0.8 or less, as described above. This configuration is suitable for ensuring the net fluidity of the encapsulating resin sheet X in the pressing step (FIG. 2B) and filling the gaps between adjacent chips 21 with the encapsulating resin, even when the ratio of the mounting height to the mounting interval of the chips 21 is large.

[0111] In addition, as described above, in the encapsulating resin sheet X, each encapsulating resin layer has an average linear thermal expansion coefficient of 20 ppm / °C or less in the temperature range from -40°C to the glass transition temperature after curing. Such a configuration is suitable for suppressing internal stress in each encapsulating resin layer in the encapsulating resin sheet X that has been cured through high-temperature heating and then cooled to, for example, room temperature. The suppression of internal stress in each encapsulating resin layer after curing is suitable for suppressing warpage in an electronic component device as a resin encapsulant manufactured using the encapsulating resin sheet X. The suppression of warpage is suitable for suppressing detachment of the cured resin portion formed from the encapsulating resin sheet X from the substrate S.

[0112] As described above, the sealing resin layer 11 preferably contains a layered silicate compound. Such a configuration is suitable for increasing the viscosity of the sealing resin layer 11 and for developing a thixotropic property in which the viscosity of the sealing resin layer 11 is lower when the sealing resin layer 11 is subjected to a pressing force than when the sealing resin layer 11 is not subjected to the pressing force. The development of the thixotropic property in the sealing resin layer 11 is suitable for the sealing resin layer 11 and the sealing resin layer 12 to soften and flow under the pressing force in the pressing step (FIG. 2B), and to deform in accordance with the outer shape of the chip 21. The increase in the viscosity of the sealing resin layer 11 is suitable for suppressing the viscosity reduction of the sealing resin layer 11 caused by the temperature rise in the curing step (FIG. 2C), and for suppressing the excessive intrusion of the sealing resin into the gap G.

[0113] The encapsulating resin sheet X may further include at least one other encapsulating resin layer between the encapsulating resin layers 11 and 12. Fig. 3 exemplarily shows a case where the encapsulating resin sheet X further includes an encapsulating resin layer 13 between the encapsulating resin layers 11 and 12. The encapsulating resin layer 13 is in direct contact with the encapsulating resin layers 11 and 12. It is preferable that the encapsulating resin sheet X further includes an encapsulating resin layer between the encapsulating resin layers 11 and 12 in order to prevent the encapsulating resin layer 12 from flowing toward the electronic component chip in the above-mentioned pressing step.

[0114] The sealing resin layer 13 is a layer formed from a third thermosetting composition. The third thermosetting composition includes a third thermosetting resin and a third inorganic filler. That is, the sealing resin layer 13 includes a third thermosetting resin and a third inorganic filler. The sealing resin layer 13 is in a semi-cured state (B-stage state).

[0115] The third thermosetting resin may be, for example, the first thermosetting resin described above. The content of the third thermosetting resin in the third thermosetting composition is preferably 3% by mass or more, more preferably 3.5% by mass or more. The content of the third thermosetting resin in the third thermosetting composition is preferably 30% by mass or less, more preferably 25% by mass or less.

[0116] The third thermosetting resin preferably contains an epoxy resin. Examples of the epoxy resin include the epoxy resins described above for the first thermosetting composition, and preferably a bifunctional epoxy resin is used, more preferably a bisphenol A type epoxy resin and / or a bisphenol F type epoxy resin. The preferred range of the epoxy equivalent of the epoxy resin in the third thermosetting composition is the same as that described above as the preferred range of the epoxy equivalent of the epoxy resin in the first thermosetting composition.

[0117] When an epoxy resin is used as the third thermosetting resin, the third thermosetting resin preferably contains a phenolic resin as a curing agent for the epoxy resin. The phenolic resin preferably includes a novolac type phenolic resin and a triphenylmethane type phenolic resin. In the third thermosetting composition, the amount of hydroxyl groups in the phenolic resin as a curing agent relative to one equivalent of the epoxy group of the epoxy resin is the same as the amount of hydroxyl groups in the phenolic resin as a curing agent relative to one equivalent of the epoxy group of the epoxy resin described above for the first thermosetting composition. In addition, the amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin in the third thermosetting composition is the same as the amount of the phenolic resin as a curing agent relative to 100 parts by mass of the epoxy resin described above for the first thermosetting composition.

[0118] The third thermosetting composition preferably contains a curing accelerator. Examples of the curing accelerator include the curing accelerators described above for the first thermosetting composition. The amount of the curing accelerator per 100 parts by mass of the third thermosetting resin is, for example, 0.05 parts by mass or more and, for example, 5 parts by mass or less.

[0119] Examples of the third inorganic filler include the first inorganic filler (layered silicate compound, inorganic filler other than layered silicate compound) described above in relation to the first thermosetting composition.

[0120] The content of the layered silicate compound in the third thermosetting composition (i.e., the content of the layered silicate compound in the encapsulating resin layer 13) is preferably 1 mass% or more, more preferably 1.2 mass% or more, and even more preferably 1.4 mass% or more. Such a configuration is suitable for increasing the viscosity of the encapsulating resin layer 13 while allowing the encapsulating resin layer 13 to exhibit thixotropic properties in which the viscosity is lower when the encapsulating resin layer 13 is subjected to a pressing force than when it is not subjected to the pressing force. From the viewpoint of avoiding excessive thickening of the third thermosetting composition, the content of the layered silicate compound in the third thermosetting composition is preferably 6 mass% or less, more preferably 5 mass% or less, and even more preferably 4 mass% or less.

[0121] As the inorganic filler other than the layered silicate compound in the third thermosetting composition, preferably, a silicon compound other than the layered silicate compound is used, more preferably, silica is used.The shape of the inorganic filler can be, for example, approximately spherical, approximately plate-like, approximately needle-like, and irregular, and approximately spherical is preferred.The average particle size of the inorganic filler other than the layered silicate compound is the same as the average particle size of the inorganic filler other than the layered silicate compound in the first thermosetting composition.

[0122] The content of the inorganic filler other than the layered silicate compound in the third thermosetting composition is preferably 73 mass% or more, more preferably 76 mass% or more, and even more preferably 78 mass% or more. Such a configuration is suitable for suppressing expansion and contraction due to temperature changes in the sealing resin layer 13. The content is preferably 90 mass% or less, more preferably 85 mass% or less, and even more preferably 83 mass% or less. Such a configuration is suitable for avoiding excessive thickening of the third thermosetting composition and ensuring the fluidity of the sealing resin layer 13 in the above-mentioned pressing step.

[0123] The content ratio R3 of the third inorganic filler in the third thermosetting composition (encapsulating resin layer 13) is preferably 75 mass% or more, more preferably 78 mass% or more, and even more preferably 80 mass% or more. Such a configuration is preferable for suppressing expansion and contraction due to temperature change in the encapsulating resin layer 13, and is preferable for achieving an average linear thermal expansion coefficient of 20 ppm / °C or less. The content ratio R3 is preferably 90 mass% or less, more preferably 87 mass% or less, and even more preferably 85 mass% or less. Such a configuration is suitable for avoiding excessive thickening of the third thermosetting composition and ensuring the fluidity of the encapsulating resin layer 13 in the above-mentioned pressing process.

[0124] The ratio of the layered silicate compound in the third inorganic filler is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more. The ratio is preferably 8 mass% or less, more preferably 7 mass% or less, and even more preferably 6.5 mass% or less. These configurations are suitable for realizing a good balance between suppressing expansion and contraction due to temperature changes in the sealing resin layer 13, ensuring fluidity in the above-mentioned pressing process, and expressing the above-mentioned thixotropy.

[0125] The third thermosetting composition may include other components as described above with respect to the first thermosetting composition.

[0126] 3 can be produced by, for example, forming the encapsulating resin layers 11, 12, and 13, and then laminating the encapsulating resin layer 11, the encapsulating resin layer 13, and the encapsulating resin layer 12 in this order. The encapsulating resin layer 13 can be formed by the same method as described above for the encapsulating resin layers 11 and 12.

[0127] The ratio of the total thickness of the encapsulating resin layer H1 and the encapsulating resin layer 13 to the total thickness of the encapsulating resin sheet X is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. Such a configuration is preferable for preventing the encapsulating resin layer 12 from flowing toward the electronic component chips in the above-mentioned pressing process.

[0128] The ratio of the total thickness of the sealing resin layer H1 and the sealing resin layer 13 H3 to the total thickness of the sealing resin sheet X is 0.82 or less, and preferably 0.8 or less. Such a configuration is suitable for ensuring the net fluidity of the sealing resin sheet X in the above-mentioned pressing process and filling the gaps between adjacent chips with the sealing resin.

[0129] The minimum melt viscosity of the encapsulating resin layer 13 is preferably 120 kPa·s or more, more preferably 150 kPa·s or more, and is preferably 260 kPa·s or less, more preferably 240 kPa·s or less. Such a configuration is preferable for ensuring the net fluidity of the encapsulating resin sheet X in the above-mentioned pressing step and filling the gaps between adjacent chips with the encapsulating resin.

[0130] The encapsulating resin layer 13 has an average linear thermal expansion coefficient Z3 of 20 ppm / ° C. or less in a temperature range from −40° C. to the glass transition temperature after being cured by heating at 150° C. for 1 hour. Such a configuration is suitable for suppressing internal stress in the encapsulating resin layer 13 in the encapsulating resin sheet X that has been cured through high-temperature heating and then cooled to, for example, room temperature. EXAMPLES

[0131] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples. In addition, the specific numerical values ​​of the blending amount (content), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "not more than" or "less than") or lower limit (a numerical value defined as "not less than" or "more than") of the corresponding blending amount (content), physical property values, parameters, etc. described in the above "Form for carrying out the invention".

[0132] [Preparation Examples 1 to 8] Each resin film of Preparation Examples 1 to 8 for forming an encapsulating resin layer was prepared as follows. First, each component was mixed according to the formulation shown in Table 1 to prepare a composition (varnish) (in Table 1, the unit of each numerical value expressing the composition is a relative "part by mass"). Next, the composition was applied to a polyethylene terephthalate film (PET film) whose surface had been subjected to silicone release treatment to form a coating film. Next, this coating film was heated and dried at 120°C for 2 minutes to prepare a resin film with a thickness of 50 μm on the PET film (the resin film was in a B-stage state). Furthermore, the resin film of Preparation Example 2 was also prepared as a resin film with a thickness of 40 μm, and the resin film of Preparation Example 5 was also prepared as a resin film with a thickness of 40 μm and a resin film with a thickness of 20 μm.

[0133] [Table 1]

[0134] The components used in Preparation Examples 1 to 8 are as follows. Epoxy resin E1: DIC's "EPICLON EXA-4850-150" (bisphenol A type epoxy resin, molecular weight 900, epoxy equivalent 450g / eq, liquid at room temperature) Epoxy resin E2: "YSLV-80XY" manufactured by Nippon Steel Chemical Co., Ltd. (bisphenol F type epoxy resin, high molecular weight epoxy resin, epoxy equivalent 191g / eq, solid at room temperature, softening point 80℃) Epoxy resin E3: "EPPN-501HY" manufactured by Nippon Kayaku Co., Ltd. (multifunctional epoxy resin, epoxy equivalent 169g / eq, solid at room temperature, softening point 60℃) Phenolic resin F1: Gun-ei Chemical's "LVR-8210DL" (novolac type phenolic resin, latent hardener, hydroxyl equivalent 104g / eq, solid at room temperature, softening point 60°C) Phenolic resin F2: Meiwa Kasei's "MEHC-7851SS" (phenol aralkyl resin, latent hardener, hydroxyl equivalent 201-220g / eq, solid at room temperature, softening point 64-85°C) Phenolic resin F3: Gun-ei Chemical Co., Ltd.'s "TPM-100" (triphenylmethane type phenolic resin, latent hardener, hydroxyl equivalent 98g / eq, solid at room temperature, softening point 108.2℃) Acrylic resin: "HME-2006M" manufactured by Negami Chemical Industries Co., Ltd. (acrylic resin containing carboxyl groups, acid value 32 mg KOH / g, weight average molecular weight 1.29 million, glass transition temperature (Tg) -13.9°C, methyl ethyl ketone solution with solid content concentration of 20% by mass) Silane coupling agent: Shin-Etsu Chemical's "KBM-403" (3-glycidoxypropyltrimethoxysilane) Layered silicate compound: "Esben NX" manufactured by Hojun Co., Ltd. (organic bentonite whose surface is modified with dimethyl distearyl ammonium) First silica particles: "FB-8SM" manufactured by Denka Co., Ltd. (spherical silica particles, average particle size 7.0 μm, no surface treatment) Second silica particles: Admatechs' "SC220G-SMJ" (spherical silica particles, average particle size 0.5 μm) surface-treated with 3-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical's "KBM-503") (the silane coupling agent used for surface treatment was 1 part by mass per 100 parts by mass of silica particles). Curing accelerator: "2PHZ-PW" (2-phenyl-4,5-dihydroxymethylimidazole) manufactured by Shikoku Chemical Industry Co., Ltd. Pigment: Carbon black: Mitsubishi Chemical #20, average particle size 50 nm Solvent: Methyl ethyl ketone

[0135] [Examples 1 to 9 and Comparative Examples 1 to 5] The encapsulating resin sheets of Examples 1 to 9 and Comparative Examples 1 to 5 were produced as follows.

[0136] In producing the sealing resin sheet of Example 1, two sheets of the resin film (thickness 50 μm) of Production Example 1 were laminated together to form a first sealing resin layer (thickness 100 μm), and three sheets of the resin film (thickness 50 μm) of Production Example 5 were laminated together to form a second sealing resin layer (thickness 150 μm), and these first and second sealing resin layers were laminated together. The lamination temperature was 80° C. (The same applies to the lamination described below).

[0137] In producing the sealing resin sheet of Example 2, three sheets of the resin film (thickness 50 μm) of Production Example 1 were bonded together to form a first sealing resin layer (thickness 150 μm), and two sheets of the resin film (thickness 50 μm) of Production Example 5 were bonded together to form a second sealing resin layer (thickness 100 μm), and these first and second sealing resin layers were bonded together.

[0138] In producing the sealing resin sheet of Example 3, four sheets of the resin film (thickness 50 μm) of Production Example 1 were bonded together to form a first sealing resin layer (thickness 200 μm), and the resin film (thickness 50 μm) of Production Example 5 was prepared as a second sealing resin layer, and these first and second sealing resin layers were bonded together.

[0139] In producing the sealing resin sheet of Example 4, two sheets of the resin film (thickness 50 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 100 μm), and three sheets of the resin film (thickness 50 μm) of Production Example 5 were bonded together to form a second sealing resin layer (thickness 150 μm), and these first and second sealing resin layers were bonded together.

[0140] In producing the sealing resin sheet of Example 5, three sheets of the resin film (thickness 50 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 150 μm), and two sheets of the resin film (thickness 50 μm) of Production Example 5 were bonded together to form a second sealing resin layer (thickness 100 μm), and these first and second sealing resin layers were bonded together.

[0141] In producing the sealing resin sheet of Example 6, four sheets of the resin film (thickness 50 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 200 μm), and the resin film (thickness 50 μm) of Production Example 5 was prepared as a second sealing resin layer, and these first and second sealing resin layers were bonded together.

[0142] In producing the sealing resin sheet of Example 7, two sheets of the resin film (thickness 40 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 80 μm), and three sheets of the resin film (thickness 40 μm) of Production Example 5 were bonded together to form a second sealing resin layer (thickness 120 μm), and these first and second sealing resin layers were bonded together.

[0143] In producing the sealing resin sheet of Example 8, three sheets of the resin film (thickness 50 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 150 μm), and two sheets of the resin film (thickness 50 μm) of Production Example 8 were bonded together to form a second sealing resin layer (thickness 100 μm), and these first and second sealing resin layers were bonded together.

[0144] In producing the sealing resin sheet of Example 9, two sheets of the resin film (thickness 50 μm) of Production Example 2 were bonded together to form a first sealing resin layer (thickness 100 μm), the resin film (thickness 50 μm) of Production Example 1 was prepared as a third sealing resin layer, and two sheets of the resin film (thickness 50 μm) of Production Example 5 were bonded together to form a second sealing resin layer (thickness 100 μm), and these first, third and second sealing resin layers were bonded together in this order.

[0145] In preparing the sealing resin sheet of Comparative Example 1, two resin films (thickness 50 μm) of Preparation Example 1 were bonded together to form a first sealing resin layer (thickness 100 μm), and a resin film (thickness 20 μm) of Preparation Example 5 was prepared as a second sealing resin layer, and these first and second sealing resin layers were bonded together.

[0146] In preparing the sealing resin sheet of Comparative Example 2, two sheets of the resin film (thickness 40 μm) of Preparation Example 2 were bonded together to form a first sealing resin layer (thickness 80 μm), and four sheets of the resin film (thickness 50 μm) of Preparation Example 5 were bonded together to form a second sealing resin layer (thickness 200 μm), and these first and second sealing resin layers were bonded together.

[0147] In preparing the sealing resin sheet of Comparative Example 3, two sheets of the resin film (thickness 50 μm) of Preparation Example 3 were bonded together to form a first sealing resin layer (thickness 100 μm), and three sheets of the resin film (thickness 50 μm) of Preparation Example 6 were bonded together to form a second sealing resin layer (thickness 150 μm), and these first and second sealing resin layers were bonded together.

[0148] In preparing the sealing resin sheet of Comparative Example 4, two sheets of the resin film (thickness 50 μm) of Preparation Example 4 were bonded together to form a first sealing resin layer (thickness 100 μm), and three sheets of the resin film (thickness 50 μm) of Preparation Example 6 were bonded together to form a second sealing resin layer (thickness 150 μm), and these first and second sealing resin layers were bonded together.

[0149] In preparing the sealing resin sheet of Comparative Example 5, two sheets of the resin film (thickness 50 μm) of Preparation Example 3 were bonded together to form a first sealing resin layer (thickness 100 μm), and three sheets of the resin film (thickness 50 μm) of Preparation Example 7 were bonded together to form a second sealing resin layer (thickness 150 μm), and these first and second sealing resin layers were bonded together.

[0150] <Minimum melt viscosity> For each of the first sealing resin layers of the sealing resin sheets of Examples 1 to 9 and Comparative Examples 1 to 5, the minimum melt viscosity was measured as follows.

[0151] First, for each of the sealing resin sheets of Examples 1 to 9 and Comparative Examples 1 to 5, 20 sheets of the above-mentioned resin film (thickness 50 μm) forming the first sealing resin layer were laminated together to prepare a sample film (thickness 1 mm) for measurement. Next, the viscoelasticity measurement of the sample film was carried out. In this measurement, a rheometer (trade name "HAAKE MARS III", manufactured by Thermo Fisher Scientific) was used, and the sample film was sandwiched between a heating plate in the device and a parallel plate (diameter 8 mm) arranged parallel to the heating plate, with a plate gap of 0.8 mm. Then, the viscosity of the sample film was measured under the conditions of a frequency of 1 Hz, a strain value of 0.005%, a temperature range of 50°C to 90°C, and a heating rate of 30°C / min. The viscosity at the temperature showing the lowest viscosity in the measurement temperature range is shown in Tables 2 to 4 as the minimum melt viscosity (kPa·s).

[0152] <Average linear thermal expansion coefficient> For each of the encapsulating resin layers of each of the encapsulating resin sheets of Examples 1 to 9 and Comparative Examples 1 to 5, the average linear thermal expansion coefficient after curing was examined.

[0153] First, a sheet piece (width 4.5 mm × length 16 mm) was cut out from the encapsulating resin sheet. Next, the sheet piece was cured by heating at 150 ° C for 1 hour. Next, the cured encapsulating resin layer other than the cured encapsulating resin layer (first encapsulating resin layer, second encapsulating resin layer, or third encapsulating resin layer) to be measured for thermal expansion coefficient was removed by mechanical polishing from the cured sheet piece so that the cured encapsulating resin layer other than the layer to be measured for thermal expansion coefficient remained. For the mechanical polishing, a polishing machine (product name "EcoMet250", manufactured by BUEHLER) was used. Next, the linear thermal expansion coefficient of the cured encapsulating resin layer thus prepared was measured under the following conditions (TMA measurement) by a thermomechanical analyzer (TMA). From the measurement results, the glass transition temperature and the average linear thermal expansion coefficient in the temperature range from -40 ° C to the glass transition temperature were obtained for the cured encapsulating resin layer. The average linear thermal expansion coefficients Z1, Z2, and Z3 (ppm / ° C.) after curing of the first to third encapsulating resin layers are shown in Tables 2 to 4.

[0154] (Measurement conditions) Thermomechanical analyzer (TMA): Q400 TMA, manufactured by TA Instruments Japan Mode: Tensile mode Heating rate: 1℃ / min Modulation: ±5.000℃ / 300sec Measurement temperature range: -40℃ to 260℃

[0155] <Evaluation of penetration length> The hollow sealing property of each of the sealing resin sheets of Examples 1 to 9 and Comparative Examples 1 to 5 was examined. Specifically, the results are as follows.

[0156] First, as shown in Fig. 4A, a sample sheet X' (10 mm long x 10 mm wide) was prepared from the encapsulating resin sheet of each Example and Comparative Example. The sample sheet X' cut out from the encapsulating resin sheet of each Example 1 to 8 and Comparative Examples 1 to 5 includes a first encapsulating resin layer 11 and a second encapsulating resin layer 12 in order in the thickness direction. The sample sheet X' cut out from the encapsulating resin sheet of Example 9 includes a first encapsulating resin layer 11, a third encapsulating resin layer (not shown), and a second encapsulating resin layer 12 in order in the thickness direction.

[0157] Meanwhile, a dummy chip mounting substrate was prepared as the workpiece W. The dummy chip mounting substrate includes a glass substrate S and a plurality of dummy chips 21' (3 mm x 3 mm x 250 μm thick). The dummy chips 21' are bonded to the substrate S via bumps 22, facing the substrate S across a gap G. The mounting height of the dummy chips 21' is 300 μm. The mounting interval of the dummy chips 21' is 300 μm. The length from the substrate S to the dummy chips 21' in the gap G (the separation distance between the substrate S and the dummy chips 21') is 50 μm.

[0158] Next, as shown in FIG. 4B, the above-mentioned workpiece W and sample sheet X' were placed between a first press plate P1 and a second press plate P2 of a flat plate press machine.

[0159] Next, as shown in FIG. 4C, the dummy chip 21′ on the substrate S was sealed with the sample sheet X′ by a vacuum plate press under sealing conditions of a temperature of 70° C., a vacuum degree of 1.6 kPa or less, a pressure of 0.1 MPa, and a pressurizing time of 40 seconds (pressing process).

[0160] Next, as shown in FIG. 4D, the sample sheet X' was cured by heating at 150° C. for 1 hour under atmospheric pressure.

[0161] Then, as shown in the enlarged view of FIG. 4D, the side surface 21b of the dummy chip 21' was used as a reference, and the length of penetration of the sealing resin (part of the first sealing resin layer 11) derived from the sample sheet X' from the side surface 21b into the gap G between the dummy chip 21' and the substrate S was measured as the penetration length L (μm). The results are shown in Tables 2 to 4. A negative penetration length L means that a space (see the thick dashed line in FIG. 4D) is formed that protrudes outward from the side surface 21b of the dummy chip 21'. The absolute value of the negative value corresponds to the protruding length of that space.

[0162] According to each of the sealing resin sheets of Examples 1 to 9, the penetration length L was not less than 0 μm and not more than 50 μm, and the dummy chip 21′ could be appropriately sealed in a hollow space.

[0163] In contrast, in the sealing resin sheet of Comparative Example 1, the gaps between the dummy chips 21' could not be sufficiently filled in the pressing process (FIG. 4C). Specifically, a void (gap) was formed between the substrate S and the sealing resin sheet X' in the region between the dummy chips 21'. In the sealing resin sheet of Comparative Example 2, a break occurred in the first sealing resin layer 11 in the pressing process. Therefore, a part of the second sealing resin layer 12 passed through the broken portion of the first sealing resin layer 11 and flowed into the dummy chip 21' side, and the flowed-in resin flowed between the dummy chip 21' and the first sealing resin layer 11 to reach the gap G and over-penetrated into the gap G. In each of the sealing resin sheets of Comparative Examples 3 and 5, the first sealing resin layer 11 over-penetrated into the gap G between the substrate S and the dummy chip 21' in the pressing process. The sealing resin sheet of Comparative Example 4 had poor fluidity in the pressing step, and as a result, the gap G could not be appropriately sealed (the penetration length L was a negative value).

[0164] [Table 2]

[0165] [Table 3]

[0166] [Table 4] [Explanation of symbols]

[0167] X Sealing resin sheet D Thickness direction 11 Sealing resin layer (first sealing resin layer) 12 Sealing resin layer (second sealing resin layer) 13 Sealing resin layer (third sealing resin layer) W work S-substrate Sa mounting surface 21 Chips 21a Main surface 21b Side 22 Bump electrode P1 First press plate P2 Second press plate

Claims

1. A sealing resin sheet including a first sealing resin layer and a second sealing resin layer in this order in a thickness direction, the first sealing resin layer includes a first thermosetting resin and a first inorganic filler, and has an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to a glass transition temperature after curing; the second sealing resin layer includes a second thermosetting resin and a second inorganic filler, and has an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40°C to a glass transition temperature after curing; a content ratio of the first inorganic filler in the first sealing resin layer and a content ratio of the second inorganic filler in the second sealing resin layer are different, a ratio of a thickness of the first sealing resin layer to a total thickness of the sealing resin sheet is 0.37 or more and 0.82 or less.

2. The sealing resin sheet according to claim 1 , wherein the first sealing resin layer has a thickness of 90 μm or more.

3. The sealing resin sheet according to claim 1 or 2, wherein the first sealing resin layer has a minimum melt viscosity of 120 kPa·s or more.

4. The sealing resin sheet according to claim 1 , wherein the first sealing resin layer has a minimum melt viscosity of 260 kPa·s or less.

5. a third sealing resin layer between the first sealing resin layer and the second sealing resin layer, The third sealing resin layer contains a third thermosetting resin and a third inorganic filler, and has an average linear thermal expansion coefficient of 20 ppm / °C or less in a temperature range from -40 °C to a glass transition temperature after curing. The sealing resin sheet according to any one of claims 1 to 4.

6. 6. The sealing resin sheet according to claim 5, wherein the third sealing resin layer is in direct contact with the first sealing resin layer, and a ratio of a total thickness of the first sealing resin layer and a thickness of the third sealing resin layer to a total thickness of the sealing resin sheet is 0.4 to 0.

82.

7. The encapsulating resin sheet according to claim 1 , wherein a content ratio of the inorganic filler in each of the encapsulating resin layers is 75 mass % or more.

8. The encapsulating resin sheet according to claim 1 , wherein a content ratio of the inorganic filler in each of the encapsulating resin layers is 90 mass % or less.

9. A substrate; an electronic component chip mounted on the substrate in a manner facing the substrate with a gap therebetween; 9. An electronic component device comprising: a cured resin portion formed from the sealing resin sheet according to claim 1, said cured resin portion sealing said electronic component chip and said gap.

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