Thermosetting sealing sheet and method for manufacturing sealing body for mounting structure

Abstract

The present invention relates to a thermosetting sealing sheet which includes at least a first layer and is used for sealing a mounting structure including a first circuit member and a plurality of second circuit members mounted on the first circuit member. The first layer is composed of a first thermosetting resin composition. The first thermosetting resin composition contains a first filler. The first filler includes non-spherical particles. A gap is interposed between the first circuit member and the second circuit member. The average distance L between the first circuit member and the second circuit member and the average value Dma of the maximum diameters Dm of the non-spherical particles satisfy Dma / L≥0.1.

Description

Thermosetting sealing sheet and method for manufacturing sealing body of mounting structure CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2023-205640, filed on December 5, 2023, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing a thermosetting sealing sheet and a sealing body of a mounting structure.

[0003] Patent Document 1 proposes "a clay-like thermosetting sealing resin sheet formed from a resin composition containing a liquid thermosetting resin and a non-conductive filler as essential components, wherein the resin composition contains 10 to 90 mass % of the non-conductive filler, and the thermosetting sealing resin sheet is characterized in that it undergoes plastic deformation when subjected to an external force at room temperature."

[0004] Patent Document 2 proposes "an encapsulating resin sheet for encapsulating an element, which contains a thermosetting resin, a layered silicate compound, and a thermoplastic resin, wherein the thermoplastic resin contains an acrylic resin, the acrylic resin has a carboxyl group, and the acid value of the acrylic resin is 18 or more."

[0005] On the other hand, Patent Document 3 proposes a "resin composition containing, as essential components, plate-like alumina (A) containing silicon as an atom and / or an inorganic compound, and a resin (B)."

[0006] JP 2008-177432 A JP 2021-97206 A International Publication No. 2019 / 194160

[0007] A gap may be provided between a circuit board (first circuit member) and an electronic component (second circuit member) mounted on the circuit board. For example, a SAW chip used for noise removal filters a desired frequency using surface waves propagating on a piezoelectric substrate (piezoelectric body). Therefore, a space is required between the circuit board on which the SAW chip is mounted and the electrodes on the piezoelectric body. When sealing such circuit members, a sealant must seal the circuit members without filling the gap.

[0008] One aspect of the present invention relates to a thermosetting encapsulating sheet that includes at least a first layer and is used to encapsulate a mounting structure that includes a first circuit member and a plurality of second circuit members mounted on the first circuit member, wherein the first layer is made of a first thermosetting resin composition, the first thermosetting resin composition includes a first filler, and the first filler includes non-spherical particles, a gap is present between the first circuit member and the second circuit member, and an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1.

[0009] Another aspect of the present invention relates to a method for manufacturing a sealed body of a mounting structure, the method comprising: preparing a mounting structure including a first circuit member and a plurality of second circuit members mounted on the first circuit member, with a gap between the first circuit member and the second circuit member; preparing a thermosetting encapsulating sheet including at least a first layer, the first layer being composed of a first thermosetting resin composition, the first thermosetting resin composition including a first filler, and the first filler including non-spherical particles; arranging the thermosetting encapsulating sheet on the mounting structure so that the first layer faces the second circuit member; and sealing the second circuit member by pressing the thermosetting encapsulating sheet against the first circuit member and heating it, wherein an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1.

[0010] The thermosetting sealing sheet according to the present disclosure is less likely to penetrate into a space between the first circuit member and the second circuit member, if such a space exists.

[0011] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0012] Fig. 1 is a cross-sectional view schematically showing a mounting structure according to one embodiment of the present invention. Fig. 2 is an enlarged view of a portion of the mounting structure of Fig. 1. Fig. 3 is a cross-sectional view schematically showing a thermosetting sealing sheet according to one embodiment of the present invention. Fig. 4 is an explanatory view schematically showing a method for manufacturing a mounting structure according to one embodiment of the present invention.

[0013] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit.

[0014] In this specification, the expression "X is composed of Y" is not limiting, and X may or may not include elements other than Y. In other words, the expression "X is composed of Y" can be replaced with expressions such as "X includes Y" or "X consists of Y." 50% by mass or more of X may be Y.

[0015] The present disclosure relates to the following. [Technology 1] A thermosetting encapsulating sheet used to encapsulate a mounting structure including at least a first layer, the thermosetting encapsulating sheet including a first circuit member and a plurality of second circuit members mounted on the first circuit member, wherein the first layer is composed of a first thermosetting resin composition, the first thermosetting resin composition includes a first filler, the first filler includes non-spherical particles, gaps are present between the first circuit member and the second circuit member, and an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1. When encapsulating the mounting structure, the thermosetting encapsulating sheet according to Technology 1 orients flat surfaces of two or more of the non-spherical particles so as to intersect with the direction of intrusion of the thermosetting encapsulating sheet into the gaps, thereby restricting intrusion of the thermosetting encapsulating sheet into the gaps. [Technology 2] The thermosetting encapsulant sheet according to Technology 1, wherein the non-spherical particles have an average aspect ratio of 1.5 or more. [Technology 3] The thermosetting encapsulant sheet according to Technology 1 or 2, wherein the non-spherical particles are plate-like particles. [Technology 4] The thermosetting encapsulant sheet according to Technology 3, wherein the plate-like particles have an average thickness of 3 μm or less or 1 μm or less. [Technology 5] The thermosetting encapsulant sheet according to any one of Technology 1 to 4, wherein the content of the first filler in the first layer is 35 vol% to 91 vol%. [Technology 6] The thermosetting encapsulant sheet according to any one of Technology 1 to 5, wherein the first filler further comprises first spherical particles. [Technology 7] The thermosetting encapsulant sheet according to Technology 6, wherein the average aspect ratio of the first spherical particles is 1.1 or less. [Technology 8] The thermosetting encapsulant sheet according to Technology 6 or 7, wherein the content of the non-spherical particles in the first filler is 1 vol% to 50 vol%. [Technology 9] The thermosetting sealing sheet according to any one of Technologies 1 to 8, wherein the thermosetting sealing sheet has the first layer and a second layer laminated on the first layer, the second layer being made of a second thermosetting resin composition, the second thermosetting resin composition containing a second filler, and the second filler containing second spherical particles.[Technology 10] A method for manufacturing a sealed mounting structure, comprising: a step of preparing a mounting structure comprising a first circuit member and a plurality of second circuit members mounted on the first circuit member, wherein a gap is interposed between the first circuit member and the second circuit member; a step of preparing a thermosetting encapsulating sheet comprising at least a first layer, the first layer being made of a first thermosetting resin composition, the first thermosetting resin composition including a first filler, and the first filler including non-spherical particles; a step of arranging the thermosetting encapsulating sheet on the mounting structure so that the first layer faces the second circuit member; and a sealing step of pressing the thermosetting encapsulating sheet against the first circuit member and heating it to seal the second circuit member, wherein an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1. In a method for manufacturing a sealed body of a mounting structure according to Technology 10, when sealing the mounting structure, flat surfaces of two or more of the non-spherical particles are oriented so as to intersect with the direction of penetration into the gaps in the thermosetting sealing sheet, thereby restricting penetration of the thermosetting sealing sheet into the gaps. [Technology 11] A method for manufacturing a sealed body of a mounting structure according to Technology 10, wherein the non-spherical particles have an average aspect ratio of 1.5 or more. [Technology 12] A method for manufacturing a sealed body of a mounting structure according to Technology 10 or 11, wherein the non-spherical particles are plate-like particles. [Technology 13] A method for manufacturing a sealed body of a mounting structure according to Technology 12, wherein the plate-like particles have an average thickness of 3 μm or less or 1 μm or less. [Technology 14] A method for manufacturing a sealed body of a mounting structure according to any one of Technology 10 to 13, wherein the content of the first filler in the first layer is 35 vol% to 91 vol%. [Technology 15] A method for manufacturing a sealed body of a mounting structure according to any one of Techniques 10 to 14, wherein the first filler further contains first spherical particles. [Technology 16] A method for manufacturing a sealed body of a mounting structure according to Technique 15, wherein the average aspect ratio of the first spherical particles is 1.1 or less. [Technology 17] A method for manufacturing a sealed body of a mounting structure according to Technique 15 or 16, wherein a content of the non-spherical particles contained in the first filler is 1% by volume to 50% by volume.[Technology 18] The method for manufacturing a sealed body of a mounting structure according to any one of Technologies 10 to 17, wherein the thermosetting sealing sheet has the first layer and a second layer laminated on the first layer, the second layer being made of a second thermosetting resin composition, the second thermosetting resin composition containing a second filler, and the second filler containing second spherical particles. [Technology 19] A thermosetting encapsulating sheet used to encapsulate a mounting structure including at least a first layer, the mounting structure including a first circuit member and a plurality of second circuit members mounted on the first circuit member, wherein the first layer is made of a first thermosetting resin composition, the first thermosetting resin composition contains a first filler, the first filler contains non-spherical particles (excluding layered silicate compounds), the non-spherical particles have an average aspect ratio of 1.5 or more (excluding cases where the average aspect ratio is 15 or more), a gap is present between the first circuit member and the second circuit member, and an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1. [Technology 20] A method for manufacturing a thermosetting encapsulating sheet, comprising: a first circuit member and a plurality of second circuit members mounted on the first circuit member, with a gap between the first circuit member and the second circuit member; a thermosetting encapsulating sheet comprising at least a first layer, the first layer being made of a first thermosetting resin composition, the first thermosetting resin composition including a first filler, the first filler including non-spherical particles (excluding layered silicate compounds), the non-spherical particles having an average aspect ratio of 1.5 or more (excluding cases where the average aspect ratio is 15 or more); an arrangement step of arranging the thermosetting encapsulating sheet on the mounting structure so that the first layer faces the second circuit member; and a sealing step of pressing the thermosetting encapsulating sheet against the first circuit member and heating it to seal the second circuit member. a method for manufacturing a sealed body of a mounting structure, wherein an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1;

[0016] (Thermosetting encapsulant sheet) The thermosetting encapsulant sheet according to the present disclosure (hereinafter also referred to as "thermosetting encapsulant sheet (S)") has at least a first layer. The first layer is composed of a first thermosetting resin composition. The thermosetting encapsulant sheet (S) may have a single-layer structure or a laminated structure of two or more layers. When the thermosetting encapsulant sheet (S) has only the first layer, the thermosetting encapsulant sheet (S) has a single-layer structure. When the thermosetting encapsulant sheet (S) has a laminated structure of three or more layers, the first layer is preferably disposed as the outermost layer from the viewpoint of enhancing the effect of the first layer.

[0017] The first thermosetting resin composition contains a thermosetting resin (hereinafter also referred to as "first thermosetting resin"). At least a portion of the first thermosetting resin is in an uncured state. The first thermosetting resin may be in a semi-cured state (so-called B-stage state) in which the three-dimensional crosslinked structure is not sufficiently developed. When the first layer containing the uncured first thermosetting resin is heated, it becomes a molten first thermosetting resin composition and becomes fluid. Thereafter, the curing reaction of the first thermosetting resin proceeds.

[0018] The thermosetting encapsulating sheet (S) is used, for example, as an encapsulant for circuit members such as electronic components. The thermosetting encapsulating sheet (S) may also be used as an encapsulant for encapsulating a mounting structure. The mounting structure may include a first circuit member such as a circuit board and a plurality of second circuit members (e.g., electronic components) mounted on the first circuit member.

[0019] The first thermosetting resin composition includes a first filler, and the first filler includes non-spherical particles. The non-spherical particles broadly include particles of shapes other than spherical. When there is a gap between the first circuit member and the second circuit member, and the mounting structure is sealed with the thermosetting sealing sheet (S) while maintaining the gap, the first layer including the non-spherical particles functions effectively.

[0020] In the case of spherical particles, the particles have no directionality (anisotropy) and therefore do not have the property of being oriented in one direction by external forces. On the other hand, in the case of non-spherical particles, when an external force is applied, they have the property of being oriented in one direction (anisotropy) depending on the particle shape. When the thermosetting sealing sheet (S) is heated and the first layer becomes a molten first thermosetting resin composition, its fluidity is affected by the orientation of the non-spherical particles. For example, if the non-spherical particles have flat surfaces, the fluidity of the first thermosetting resin composition is increased in the direction in which the flat surfaces of the non-spherical particles are oriented and the fluidity of the first thermosetting resin composition in other directions is reduced. Due to this effect, if there is a gap between the first circuit member and the second circuit member, penetration of the molten first thermosetting resin composition into the gap is restricted.

[0021] The average aspect ratio Ra of the non-spherical particles may be 1.5 or more, 3 or more, 4 or more, or 4.5 or more. Non-spherical particles with such a large aspect ratio are thought to be particularly prone to orientation in the first thermosetting resin composition in a molten state. The average aspect ratio Ra may be less than 15 or 10 or less. The aspect ratio R of a non-spherical particle refers to the ratio of the maximum diameter Dm of the non-spherical particle to the maximum dimension of the non-spherical particle in a direction perpendicular to the maximum diameter Dm. The average aspect ratio Ra of the non-spherical particles may be determined as the average value of the aspect ratios R of 10 non-spherical particles using a scanning electron microscope (SEM) as described below. The average maximum diameter Dma of the non-spherical particles may be determined as the average value of the maximum diameters Dm of 10 non-spherical particles.

[0022] The non-spherical particles may be plate-like particles. The plate-like particles may have a flat shape, such as a scale or flake shape.

[0023] The average thickness of the plate-like particles may be 3 μm or less, or may be 1 μm or less. Such thin plate-like particles are thought to be particularly easy to orient in the first thermosetting resin composition in a molten state. The thickness of the plate-like particles refers to the maximum dimension in the direction perpendicular to one of the two flat surfaces of the plate-like particles. The average thickness of the plate-like particles can be determined as the average value of the thicknesses of 10 plate-like particles using a scanning electron microscope (SEM) as described below.

[0024] The average aspect ratio Ra of the plate-like particles may be 1.5 or more, 3 or more, 4 or more, or 4.5 or more. Plate-like particles with such a large aspect ratio are thought to be particularly prone to orientation in the first thermosetting resin composition in a molten state. The aspect ratio R of the plate-like particles refers to the ratio of the maximum diameter Dm of the plate-like particles to the thickness of the plate-like particles. The average aspect ratio Ra of the plate-like particles may be determined as the average value of the aspect ratios R of 10 plate-like particles using the following method using SEM images. Furthermore, the average maximum diameter Dma of the plate-like particles may be determined as the average value of the maximum diameters Dm of 10 plate-like particles. The thickness of the plate-like particles is the maximum dimension Dw of the particle in the direction perpendicular to the maximum diameter Dm of the particle (i.e., aspect ratio R = Dm / Dw). The Dma of the plate-like particles is, for example, 0.1 μm to 50 μm, and may be 1 μm to 30 μm.

[0025] The following describes how to determine the maximum diameter Dma and average aspect ratio Ra of non-spherical particles (or plate-like particles). For example, Dma and Ra can be determined by performing the following steps (1) to (5) in numerical order.

[0026] (1) A cured product of the thermosetting encapsulating sheet (S) is prepared. The cured product of the thermosetting encapsulating sheet (S) can be obtained by curing the thermosetting encapsulating sheet (S) at 150°C for 1 hour or more. In addition, the encapsulant portion of the encapsulated body of the mounting structure encapsulated with the thermosetting encapsulating sheet (S) may be used as the cured product. The encapsulated body may be a commercially available product. The curing conditions are not particularly limited as long as they are conditions under which a cured product from which a cross section described below can be obtained is obtained.

[0027] (2) The cured product or the sealed body is cut parallel to the thickness direction of the thermosetting sealing sheet (S) (or the stacking direction of the first and second circuit members in the sealed body), and the cross section is polished with a polishing device. The first circuit member, the second circuit member, and the gap between them can be observed in the cross section of the sealed body.

[0028] (3) The polished surface is observed under a scanning electron microscope (SEM) at a magnification of 2000. As an example, the observation may be performed at three locations on the polished surface, i.e., at three fields of view.

[0029] (4) The larger the size of the non-spherical particles, the greater the impact they have on the fluidity of the first thermosetting resin composition in a molten state. Therefore, in one field of view image (SEM image), 10 particles (the top 10 particles in terms of maximum diameter Dm) are selected in descending order of maximum diameter Dm, and the outer shapes of these particles are obtained. For example, the top 10 particles in terms of maximum diameter Dm may be automatically selected using image processing software or the like.

[0030] (5) From the outer peripheral shape, the maximum diameter Dm of each particle and the maximum dimension Dw of the particle in the direction perpendicular to the maximum diameter Dm are determined using image processing software or the like, and the aspect ratio R (= Dm / Dw) is calculated. The average value of the maximum diameters Dm of 10 particles (10 x N when measured in N fields of view) is calculated as Dma, and the average value of the aspect ratios R of the 10 (or 10 x N) particles is calculated as the average aspect ratio Ra.

[0031] The non-spherical particles may be polyhedral particles. That is, the non-spherical shape may be a polyhedral shape. The number of faces of the polyhedron is, for example, 4 to 19, or may be 4 to 15. The polyhedral shape may be, for example, a tetrahedron, a cube (hexahedron), an octahedron, a decahedron, a dodecahedron, or the like.

[0032] The average particle size of the polyhedral particles may be 0.1 μm to 50 μm, or may be 1 μm to 30 μm. The particle size of the polyhedral particles refers to the maximum diameter Dm of the polyhedral particles. The average particle size Dma of the polyhedral particles may be determined as the average value of the maximum diameters Dm of 10 polyhedral particles using the method using SEM images described above.

[0033] The average aspect ratio of the polyhedral particles may be, for example, 1.5 or more, or 3 or more. The aspect ratio of the polyhedral particles refers to the ratio of the maximum diameter Dm of the polyhedral particles to the maximum dimension of the polyhedral particles in a direction perpendicular to the maximum diameter Dm. The average aspect ratio of the polyhedral particles may be determined as the average value of the aspect ratios of 10 polyhedral particles using the method using SEM images described above.

[0034] The non-spherical particles may be acicular particles, which also include rod-shaped particles and short fiber-shaped particles.

[0035] The average length of the acicular particles may be 0.1 μm to 50 μm, or may be 1 μm to 30 μm. The average length of the acicular particles may be determined as the average value of the lengths of 10 acicular particles using the method using SEM images described above. The length of the acicular particles is the maximum dimension of the acicular particles and corresponds to the maximum diameter Dm. The average thickness of the acicular particles may be 3 μm or less, or may be 1 μm or less. The thickness of the acicular particles refers to the maximum dimension in the direction perpendicular to the length direction of the acicular particles. The average thickness of the acicular particles may be determined as the average value of the thicknesses of 10 acicular particles using the method using SEM images described above.

[0036] When the first particles are acicular particles, the average aspect ratio of the acicular particles may be 1.5 or more, 3 or more, 4 or more, or 4.5 or more. The aspect ratio of the acicular particles is the ratio of the length to the thickness of the acicular particles. The average aspect ratio of the acicular particles may be determined as the average value of the aspect ratios of 10 acicular particles using the above-mentioned method using SEM images.

[0037] The polyhedral particles or acicular particles may be used in greater amounts than the plate-like particles, in which case it becomes easier to control the intrusion of the sealing material into the space between the first and second circuit members.

[0038] When a gap exists between the first and second circuit members, for example, when a bump is interposed between the first and second circuit members, the average distance L between the first and second circuit members and the average value Dma of the maximum diameters Dm of the non-spherical particles must satisfy Dma / L ≥ 0.1, and preferably Dma / L ≥ 0.2. In this case, penetration of the molten first thermosetting resin composition into the gap is significantly restricted. The average distance L can be measured at a cross section obtained by simultaneously cutting the first and second circuit members on a plane parallel to the stacking direction of the first and second circuit members. The distance between the first and second circuit members can be measured at multiple cross sections (five or more cross sections) and the average value of these measurements can be used to determine L. The distance is defined as the shortest distance between the outer edge of the second circuit member and the first circuit member.

[0039] The material of the non-spherical particles may be an inorganic material, an organic material, an organic-inorganic hybrid material, a conductive material, or a non-conductive material.

[0040] The inorganic material may be a metal such as gold, silver, copper, or nickel, a metal oxide (silicon oxide (particularly silica), aluminum oxide, titanium oxide, calcium oxide, magnesium oxide, or the like), a metal carbonate (calcium carbonate, magnesium carbonate, or the like), a metal hydroxide (aluminum hydroxide, magnesium hydroxide, or the like), a metal silicate (calcium silicate, magnesium silicate, or the like), a metal nitride (boron nitride, aluminum nitride, or the like), a metal carbide (silicon carbide, or the like), talc, mica, kaolin, or the like. However, the inorganic material is not limited to these.

[0041] The organic material may be a resin such as polystyrene, polyolefin, polyester, cellulose, polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyamide, polyphenylene ether, polyparaphenylenebenzbisoxazole, polybutylene terephthalate, polyacetal, or liquid crystal polymer, but is not limited to these.

[0042] The volume content of the first filler contained in the first layer is, for example, 35% to 91% by volume, preferably 45% to 83% by volume, and more preferably 56% to 76% by volume. The volume content of the first filler contained in the first layer can be converted to "mass %" using the specific gravity of the material. For example, the specific gravity of silica particles is 2.2 g / cm ３ Therefore, the mass content of silica as the first filler contained in the first layer is, for example, 50% by mass to 95% by mass, preferably 60% by mass to 90% by mass, and more preferably 70% by mass to 85% by mass.

[0043] The volume content of the non-spherical particles contained in the first filler may be 100% by volume, or a portion of the first filler may be spherical particles (first spherical particles). When the first filler further contains first spherical particles, the volume content Cns of the non-spherical particles contained in the first filler may be 1% by volume to 50% by volume, and the volume content Cs of the first spherical particles contained in the first filler may be 50% by volume to 99% by volume. From the viewpoint of improving the fluidity of the first thermosetting resin composition (fluidity other than in the gaps between the first circuit member and the second circuit member), the volume content Cns of the non-spherical particles and the volume content Cs of the first spherical particles preferably satisfy Cns≦Cs, and may also satisfy 1.5≦Cs / Cns.

[0044] The volume content of the first filler contained in the first layer may be determined from an SEM image of the polished surface of the cured product or sealed body described above. The area of ​​the field of view of the SEM image can be divided into an area Sf occupied by the cross section of the filler and an area Sr occupied by the cross section of the material other than the filler (resin component). The ratio of the area Sf to the sum of the areas Sf and Sr can be considered to be the volume content of the first filler contained in the first layer.

[0045] The volume content of the non-spherical particles in the first filler may also be determined from an SEM image of the polished surface of the cured product or sealed body described above. The area Sf can be divided into the area Sfns occupied by the cross-sections of the non-spherical particles and the area Sfs occupied by the cross-sections of the first spherical particles. The ratio of the area Sfns to the sum of the area Sfns and the cross-sections Sfs can be considered to be the volume content of the non-spherical particles in the first filler.

[0046] The first spherical particles do not need to be perfectly spherical particles, but may be particles whose particle surfaces are mostly curved. The curved particle surfaces may have minute irregularities. For example, the first spherical particles may be ellipsoidal. Polyhedral particles having an icosahedron or higher may be considered as first spherical particles.

[0047] The average particle size Da of the first spherical particles may be 0.05 μm to 100 μm, or 0.1 μm to 30 μm. The particle size of the first spherical particles refers to the maximum diameter of the first spherical particles. As with Dma, the average particle size Da of the first spherical particles may be determined as the average value of the maximum diameters of 100 first spherical particles according to the method using SEM images described above.

[0048] The average aspect ratio of the first spherical particles may be, for example, 1.2 or less, or 1.1 or less. The aspect ratio of the first spherical particles refers to the ratio of the maximum diameter of the first spherical particles to the minimum diameter of the first spherical particles. The minimum diameter of the first spherical particles refers to the maximum dimension of the particle in a direction perpendicular to the maximum diameter of the particle. As with the average aspect ratio Ra, the average aspect ratio of the first spherical particles may be determined as the average value of the aspect ratios of 100 first spherical particles in accordance with the method using SEM images described above.

[0049] The ratio (Dma / Da) of the average value Dma of the maximum diameters Dm of the non-spherical particles to the average particle diameter Da of the first spherical particles is preferably 0.01 to 1,000, and more preferably 0.01 to 100.

[0050] In addition, when the non-spherical particles can be separated from the first thermosetting resin composition, the mode diameter D50A of the most frequent value in the volume-based particle size distribution of the non-spherical particles measured with a laser diffraction / scattering particle size distribution measuring device is preferably 1 μm to 30 μm.

[0051] Furthermore, when the first spherical particles can be separated from the first thermosetting resin composition, the mode diameter D50B of the most frequent value in the volume-based particle size distribution of the first spherical particles measured with a laser diffraction / scattering particle size distribution measuring device is preferably 0.1 μm to 30 μm.

[0052] The ratio of the mode diameter D50A to the mode diameter D50B (D50A / D50B) preferably satisfies 0.01 to 1000, and more preferably satisfies 0.01 to 100. Furthermore, Dma / D50B may be 0.01 to 1000, or even 0.01 to 100, and D50A / Da may be 0.01 to 1000, or even 0.01 to 100.

[0053] The material of the first spherical particles may be an inorganic material, an organic material, an organic-inorganic hybrid material, a conductive material, or a non-conductive material. The material of the first spherical particles may be arbitrarily selected from the materials exemplified as the material of the non-spherical particles. Among them, inorganic materials are preferred, and may be metal oxides (aluminum oxide, titanium oxide, calcium oxide, magnesium oxide, silicon oxide (especially silica), etc.), metal carbonates (calcium carbonate, magnesium carbonate, etc.), metal hydroxides (aluminum hydroxide, magnesium hydroxide, etc.), metal silicates (calcium silicate, magnesium silicate, etc.), metal nitrides (aluminum nitride, etc.), metal carbides (silicon carbide, etc.), talc, mica, kaolin, etc. Typically, the first spherical particles may be spherical silica.

[0054] The thermosetting encapsulating sheet may have a first layer and a second layer laminated on the first layer. The second layer is composed of a second thermosetting resin composition. The second thermosetting resin composition includes a thermosetting resin (hereinafter also referred to as "second thermosetting resin"). At least a portion of the second layer is in an uncured state. The second layer may be in a semi-cured state (so-called B-stage state) in which the three-dimensional crosslinked structure is not sufficiently developed. When the uncured second layer is heated, it becomes molten and fluid. Thereafter, the curing reaction of the second layer proceeds. The second thermosetting resin may be the same as or different from the first thermosetting resin.

[0055] The second thermosetting resin composition includes a second filler, and the second filler includes spherical particles (second spherical particles). The second spherical particles may be arbitrarily selected from the spherical particles described as the first spherical particles. The second spherical particles may be the same as or different from the first spherical particles.

[0056] The thickness T1 of the first layer is sufficient to restrict the infiltration of the encapsulant into the space between the first and second circuit members, and is preferably greater than the average distance L between the first and second circuit members (e.g., T1 > 1.1L). The thickness T1 of the first layer is, for example, 20 μm to 300 μm, and may be 40 μm to 240 μm.

[0057] The total thickness of T1 and T2 may be, for example, 40 μm≦T1+T2≦500 μm, 50 μm≦T1+T2≦350 μm, or even 100 μm≦T1+T2≦300 μm.

[0058] The compositions of the first and second thermosetting resin compositions are not particularly limited except that they have the aforementioned configuration. The first and second thermosetting resins are not particularly limited, but may each independently be an epoxy resin, a (meth)acrylic resin, a phenolic resin, a melamine resin, a silicone resin, a urea resin, a urethane resin, a vinyl ester resin, an unsaturated polyester resin, a diallyl phthalate resin, a polyimide resin, or the like. These may be used alone or in combination of two or more. Among these, epoxy resins are preferred.

[0059] The epoxy resin is not particularly limited, but examples thereof include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AD ​​epoxy resins, hydrogenated bisphenol A epoxy resins, hydrogenated bisphenol F epoxy resins, phenol novolac epoxy resins, naphthalene epoxy resins, alicyclic aliphatic epoxy resins, and glycidyl ethers of organic carboxylic acids. These may be used alone or in combination of two or more. The epoxy resin may be a prepolymer or a copolymer of an epoxy resin with another polymer, such as a polyether-modified epoxy resin or a silicone-modified epoxy resin. Among these, bisphenol AD ​​epoxy resins, naphthalene epoxy resins, bisphenol A epoxy resins, and / or bisphenol F epoxy resins are preferred. Bisphenol A epoxy resins and bisphenol F epoxy resins are particularly preferred due to their excellent heat resistance and water resistance and low cost.

[0060] The epoxy resin may contain a monofunctional epoxy resin having one epoxy group in the molecule in an amount of approximately 0.1 to 30 mass % based on the total amount of the epoxy resin in order to adjust the viscosity of the first and second thermosetting resin compositions. Examples of such monofunctional epoxy resins that can be used include phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, ethyl diethylene glycol glycidyl ether, dicyclopentadiene glycidyl ether, and 2-hydroxyethyl glycidyl ether. These may be used alone or in combination of two or more.

[0061] The first and second thermosetting resin compositions contain a curing agent. The curing agent is not particularly limited, but examples thereof include phenolic curing agents (such as phenolic resins), dicyandiamide curing agents (such as dicyandiamide), urea curing agents, organic acid hydrazide curing agents, polyamine salt curing agents, amine adduct curing agents, acid anhydride curing agents, imidazole curing agents, amine curing agents, active ester curing agents, benzoxazine curing agents, and maleimide curing agents. These may be used alone or in combination of two or more. The type of curing agent is appropriately selected depending on the thermosetting resin. Among these, phenolic curing agents are preferred in terms of low outgassing during curing, moisture resistance, heat cycle resistance, and the like.

[0062] The amount of curing agent varies depending on the type of curing agent. When an epoxy resin is used, it is preferable to use a curing agent in an amount such that the number of equivalents of the functional group of the curing agent is 0.001 to 2 equivalents, or more preferably 0.005 to 1.5 equivalents, per equivalent of the epoxy group.

[0063] The dicyandiamide-based curing agent, urea-based curing agent, organic acid hydrazide-based curing agent, polyamine salt-based curing agent, and amine adduct-based curing agent are latent curing agents. The activation temperature of the latent curing agent is preferably 60°C or higher, more preferably 80°C or higher. The activation temperature is preferably 250°C or lower, more preferably 180°C or lower. This makes it possible to obtain a resin composition that cures rapidly at or above the activation temperature.

[0064] The first and second thermosetting resin compositions may contain a thermoplastic resin. The thermoplastic resin may have the effect of helping the thermosetting encapsulating sheet (S) having the first layer and the thermosetting encapsulating sheet (S) having the first and second layers maintain their sheet form. That is, the thermoplastic resin may be blended as a sheet-forming agent for the thermosetting resin composition. Forming the thermosetting resin composition into a sheet improves handleability in the encapsulation process.

[0065] Examples of thermoplastic resins include acrylic resins, phenoxy resins, polyolefins, polyurethanes, blocked isocyanates, polyethers, polyesters, polyimides, polyvinyl alcohols, butyral resins, polyamides, vinyl chloride, cellulose, thermoplastic epoxy resins, and thermoplastic phenolic resins. Among these, acrylic resins are preferred because of their excellent functionality as sheet-forming agents. The content of the thermoplastic resin in the first and second thermosetting resin compositions is preferably, for example, 2 to 50% by mass, and particularly preferably 4 to 25% by mass.

[0066] The form of the thermoplastic resin when added to the first and second thermosetting resin compositions is not particularly limited. The thermoplastic resin may be, for example, particles having a weight-average particle size of 0.01 to 200 μm, preferably 0.01 to 100 μm. The particles may have a core-shell structure. In this case, the core may be, for example, a polymer containing a unit derived from at least one monomer selected from the group consisting of n-, i-, and t-butyl (meth)acrylate, or a polymer containing a unit derived from another (meth)acrylate. The shell layer may be, for example, a copolymer of a monofunctional monomer such as methyl (meth)acrylate, n-, i-, or t-butyl (meth)acrylate, or (meth)acrylic acid with a polyfunctional monomer such as 1,6-hexanediol diacrylate.

[0067] The first and second thermosetting resin compositions may contain a third component other than those described above, such as a curing accelerator, a polymerization initiator, an ion catcher, a flame retardant, a pigment, a silane coupling agent, or a thixotropic agent.

[0068] 1 is a cross-sectional view schematically illustrating an example of a mounting structure according to an embodiment. The mounting structure 10 includes a first circuit member 1 (circuit board), a plurality of second circuit members 2 (electronic components) mounted on the first circuit member 1, and a sealing material 4 that seals the second circuit member 2. A gap S is formed between the first circuit member 1 and the second circuit member 2.

[0069] The encapsulant 4 is a cured product of a thermosetting encapsulating sheet having a two-layer structure including a first layer and a second layer laminated on the first layer. The encapsulant 4 is composed of a cured product 41 of the first layer (i.e., the first thermosetting resin composition) and a cured product 42 of the second layer (i.e., the second thermosetting resin composition). The encapsulant 4 seals the second circuit member 2 while maintaining the gap S.

[0070] In this embodiment, the second circuit member 2 is mounted on the first circuit member 1 via the bumps 3, but the method of mounting the second circuit member 2 on the first circuit member 1 is not limited to this.

[0071] Fig. 2 is an enlarged view of a portion of the mounting structure of Fig. 1. The first filler contains plate-like particles F, which are non-spherical particles. The plate-like particles F have a flat shape, have two opposing flat surfaces, and exhibit anisotropy, i.e., are oriented in one direction when an external force is applied. The average distance L between the first circuit member 1 and the second circuit member 2 and the maximum diameter Dm of the plate-like particles F satisfy Dma / L≧0.1.

[0072] When the molten first thermosetting resin composition is subjected to the external force required for sealing, the first thermosetting resin composition flows along the surface of the second circuit member 2. The two flat surfaces of the plate-like particles F are oriented in the flow direction of the first thermosetting resin composition. As a result, the plate-like particles F are oriented so as to block at least a portion of the gap S. Furthermore, the plate-like particles reduce the fluidity of the first thermosetting resin composition in a direction intersecting the orientation direction of the flat surfaces. Therefore, the molten first thermosetting resin composition is less likely to penetrate into the gap S between the first and second circuit members.

[0073] 3 is a cross-sectional view schematically showing the structure of a two-layer thermosetting encapsulating sheet (S) 4P having a first layer 41P and a second layer 42P. In the encapsulating step, the thermosetting encapsulating sheet (S) 4P is disposed so that the first layer 41P contacts the second circuit member 2. Therefore, the second circuit member 2 is covered with the cured product 41 of the first layer except for the surface facing the first circuit member 1.

[0074] There is no particular limitation on the manufacturing method of the thermosetting sealing sheet (S) 4P (hereinafter also referred to as "laminate sheet 4P") having the first layer 41P and the second layer 42P. The laminate sheet 4P may be formed by a lamination method in which each layer is separately manufactured and then laminated, or by a coating method in which the materials for each layer are coated in sequence.

[0075] In the lamination method, each layer is formed by a method including, for example, a step of preparing a solvent paste containing a first or second thermosetting resin composition and a solvent, or a solventless paste containing no solvent (hereinafter simply referred to as "paste"), and a layer formation step of forming each layer from each paste. The layer formation step is not particularly limited, but may involve, for example, applying each paste to a film and drying it, or molding a melt-kneaded thermosetting resin composition to a specified thickness using a heat press or rolling mill. The first layer 41P and the second layer 42P are formed by this method and then laminated in this order. If the paste contains a thermoplastic resin as a sheeting agent, the sheeting agent may be gelled. Gelling (sheeting) may be achieved by forming the paste into a thin film and then heating the thin film at a temperature below the curing temperature of the first or second thermosetting resin composition (e.g., 70 to 150°C) for 1 to 10 minutes.

[0076] In the coating method, for example, after forming the first layer 41P by the above method, a paste containing the second thermosetting resin composition is coated on the surface of the first layer 41P to form the second layer 42P. If the paste contains a thermoplastic resin as a sheet-forming agent, the sheet-forming agent may be gelled. The gelling may be carried out sequentially after forming each thin film from each paste, or after forming a laminate of thin films.

[0077] Each layer (thin film) can be formed using, for example, a die coater, a roll coater, a doctor blade, etc. In this case, it is preferable to adjust the viscosity of the paste to 10 to 10,000 mPa s. When a solvent paste is used, the solvent may be removed by drying at 70 to 150°C for 1 to 10 minutes.

[0078] 4 is an explanatory diagram schematically illustrating a method for manufacturing a mounting structure according to one embodiment (hereinafter also referred to as "manufacturing method (M)"). The manufacturing method (M) includes a first preparation step, a second preparation step, a placement step, and a sealing step. After the sealing step, a singulation step may be performed.

[0079] (First Preparation Step) The first preparation step is a step of preparing a pre-encapsulated mounting structure. The pre-encapsulated mounting structure includes a first circuit member 1 and a plurality of second circuit members 2 mounted on the first circuit member 1, with a gap S between the first circuit member 1 and the second circuit member 2. The height of the gap S roughly corresponds to the height of the bumps 3.

[0080] The first circuit member 1 may be, for example, a semiconductor element, a semiconductor package, a glass substrate, a resin substrate, a ceramic substrate, a silicon substrate, etc. The first circuit member may have a conductive material layer such as an anisotropic conductive film (ACF) or an anisotropic conductive paste (ACP) on its surface. The resin substrate may be a rigid resin substrate or a flexible resin substrate. Examples of resin substrates include epoxy resin substrates (e.g., glass epoxy substrates), bismaleimide triazine substrates, polyimide resin substrates, and fluororesin substrates. The first circuit member 1 may also be a component-embedded substrate that includes a semiconductor chip or the like inside.

[0081] The second circuit member 2 is mounted on the first circuit member 1 via, for example, bumps 3. This forms a gap S between the first circuit member 1 and the second circuit member 2. The second circuit member 2 may be an electronic component that needs to be sealed while maintaining the space S. Examples of the second circuit member 2 include a sensor chip (such as an acceleration sensor), a piezoelectric resonator chip, a quartz resonator chip, a MEMS device, an RFIC, and a SAW filter.

[0082] The bumps 3 are conductive, and the first circuit member 1 and the second circuit member 2 are electrically connected via the bumps 3. The height of the bumps 3 is not particularly limited, but may be, for example, 5 μm to 150 μm. The material of the bumps 3 is not particularly limited as long as it is conductive, and examples include copper, gold, solder, etc.

[0083] That is, the mounting structure may have a chip-on-board (CoB) structure (including chip-on-wafer (CoW), chip-on-film (CoF), and chip-on-glass (CoG)) in which a second circuit member 2 is mounted on a first circuit member 1, a chip-on-chip (CoC) structure, a chip-on-package (CoP) structure, a package-on-package (PoP) structure, or the like. The mounting structure may also be a multilayer mounting structure in which the first circuit member 1 on which the second circuit member 2 is mounted is further stacked with the first circuit member 1 and / or the second circuit member 2.

[0084] (Second preparation step) The second preparation step is a step of preparing a thermosetting sealing sheet (S) 4P. The thermosetting sealing sheet (S) 4P may include at least a first layer 41P. The first layer 41P is composed of a first thermosetting resin composition.

[0085] The thermosetting sealing sheet (S) 4P may have a second layer 42P laminated on the first layer 41 P. The second layer 42P is made of a second thermosetting resin composition.

[0086] (Placement Step) The placement step is a step of placing the thermosetting encapsulating sheet (S) 4P on the mounting structure ( FIG. 3( a) ). In the placement step, for example, the thermosetting encapsulating sheet (S) 4P is placed on the mounting structure so that the second circuit member 2 is covered by the thermosetting encapsulating sheet (S) 4P. At that time, the first layer 41P faces the second circuit member 2.

[0087] (Sealing step) The sealing step is a step in which the thermosetting sealing sheet (S) 4P is pressed against the first circuit member 1 and heated to harden it, thereby sealing the second circuit member 2 ( FIGS. 4( b) and 4(c) ). When the first layer 41P faces the second circuit member 2, the second circuit member 2 is sealed while maintaining the gap S.

[0088] The thermosetting encapsulating sheet (S) 4P may be pressed against the first circuit member 1 by a heat pressing process (compression molding process). The heat pressing process is performed, for example, while heating the thermosetting encapsulating sheet (S) 4P at a temperature lower than the curing temperature of the first (and second) thermosetting resin compositions contained in the thermosetting encapsulating sheet (S) 4P. The heat pressing may be performed to bring the first layer 41P into close contact with the surface of the second circuit member 2, and may also be performed to extend the first layer between the second circuit members 2 until it reaches the surface of the first circuit member 1, thereby improving the reliability of sealing the second circuit member 2.

[0089] The heat pressing step may be carried out under atmospheric pressure or in a reduced pressure atmosphere (e.g., 0.001 to 0.05 MPa). The heating conditions during pressing are not particularly limited and may be set appropriately depending on the pressing method and the composition of the thermosetting resin composition. The heating is carried out, for example, at 40 to 200°C (preferably 50 to 180°C) for 1 second to 300 minutes (preferably 3 seconds to 300 minutes).

[0090] Next, the molten thermosetting resin composition is heated at a curing temperature to cure the thermosetting resin composition, thereby forming the encapsulant 4. This seals the second circuit member 2. The conditions for curing the thermosetting resin composition may be set appropriately depending on the composition of the thermosetting resin composition. The thermosetting resin composition is cured, for example, at 50 to 200°C (preferably 120 to 180°C) for 1 second to 300 minutes (preferably 60 to 300 minutes).

[0091] The heat pressing step and the curing of the thermosetting resin composition may be performed separately or simultaneously. For example, the thermosetting resin composition contained in the thermosetting encapsulating sheet (S) 4P may be heat-pressed at a temperature lower than the curing temperature under a reduced pressure atmosphere, and then the reduced pressure may be released and the thermosetting resin composition may be further heated at a high temperature under atmospheric pressure to cure the thermosetting resin composition. Alternatively, the thermosetting resin composition may be heat-pressed at a temperature lower than the curing temperature of the thermosetting encapsulating sheet (S) 4P under atmospheric pressure, and then further heated at a high temperature to cure the thermosetting resin composition. Furthermore, the thermosetting resin composition may be cured during the reduced pressure by heat pressing at the curing temperature under a reduced pressure atmosphere.

[0092] (Singulation Process) The resulting mounting structure 10 may be subjected to a singulation process in which it is diced into individual second circuit members 2 (FIG. 4(d)). This results in a chip-level mounting structure (mounted chip 20). Alternatively, a singulation process may be performed in which multiple second circuit members 2 are diced to be included in one package. This results in a mounting structure with multiple chips mounted thereon, such as a multi-chip package or module.

[0093] Next, the thermosetting sealing sheet and the method for producing a mounting structure according to the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[0094] Example 1 Preparation of Thermosetting Resin Compositions The components shown below were blended in the formulations shown in Table 1 to prepare resin compositions of Preparation Examples 1 to 15 as the first resin composition or the second resin composition. The numerical values ​​in Table 1 indicate parts by mass. Thus, for example, in Preparation Example 1, 100 parts by mass of bisphenol A epoxy resin was blended with 60 parts by mass of phenol novolac resin, 25 parts by mass of acrylic resin, 3 parts by mass of curing accelerator, 3 parts by mass of carbon black, and 780 parts by mass of spherical particles (spherical silica particles 1).

[0095] The physical properties of the filler are shown in Table 2.

[0096]

[0097]

[0098] (Preparation of Thermosetting Sheet (S)) Next, the first resin composition and the second resin composition containing methyl ethyl ketone as a solvent were successively coated onto a release film to a predetermined thickness shown in Table 3, and molded by a coating method in which the solvent is evaporated by drying, to prepare thermosetting encapsulating sheets B1 and A1 to A22 each having a two-layer structure including a first layer and a second layer.

[0099]

[0100]

[0101] (Preparation of Evaluation Mounting Structure) Next, 16 dummy chips (second circuit member, 1 mm x 1 mm, height 0.2 mm) of the same size were arranged on a glass substrate (first circuit member, 50 mm square, 1 mm thick) at equal intervals (4 vertical x 4 horizontal). The chips were spaced 300 μm apart, and the chip arrangement was 4 columns x 4 rows. The specified bumps provided a distance (L) between the chips and the substrate, as shown in Table 3.

[0102] (Sealing of Evaluation Mounting Structure) Each evaluation mounting structure was sealed with each thermosetting sealing sheet by compression molding. Specifically, in a reduced pressure atmosphere of 2 hPa, the thermosetting sealing sheet was placed on the mounting structure so that the first layer faced the chip (second circuit member), and the thermosetting sealing sheet was heated at 100°C while being pressed against the first circuit member at 0.7 MPa to seal the second circuit member, and then heated in a hot air oven at 150°C for 1 hour to be cured.

[0103] The penetration distance of the sealant that penetrated between the chip and the substrate from the edge of each chip (the maximum reach of the sealant from the edge of each chip) was measured. The following evaluations are shown in Table 3. Note that the penetration distance in the evaluation below is the average value for 16 chips, and the penetration distance variation is the difference between the penetration distance of the chip with the longest penetration distance and the penetration distance of the chip with the shortest penetration distance among the 16 chips.

[0104] (Penetration distance) ◎ ... 0 um or more and 20 um or less 〇 ... Over 20 um and 35 um or less △ ... Over 35 um and 50 um or less × ... Over 50 um

[0105] (Penetration distance variation) ◎ ... 0 um or more and 15 um or less 〇 ... Over 15 um and 20 um or less × ... Over 20 um

[0106] When the thermosetting encapsulating sheets A1 to A22 of the examples were used, the penetration distance was shorter than when the thermosetting encapsulating sheet B1 of the comparative example was used. This is thought to be the effect of using non-spherical particles as part of the first filler. In fact, when the cross section of the sealed mounting structure for evaluation was observed, it was confirmed that the flat surfaces of the non-spherical particles were oriented so as to intersect with the penetration direction of the encapsulant.

[0107] The present invention is suitable for use in the field of sealing of mounting structures. The thermosetting sealing sheet according to the present invention can prevent the sealant from penetrating into the space between the circuit component and the substrate.

[0108] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0109] 10: Mounting structure 1: First circuit member 2: Second circuit member 3: Bump 4: Sealant (cured product of thermosetting sealing sheet) 4P: Sheet 41P: First layer 42P: Second layer 20: Mounting chip

Claims

1. A thermosetting encapsulating sheet used to encapsulate a mounting structure including a first circuit member and a plurality of second circuit members mounted on the first circuit member, the first layer being composed of a first thermosetting resin composition, the first thermosetting resin composition including a first filler, the first filler including non-spherical particles, a gap being present between the first circuit member and the second circuit member, an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfying Dma / L≧0.1, and when encapsulating the mounting structure, the thermosetting encapsulating sheet is configured such that flat surfaces of two or more of the non-spherical particles are oriented so as to intersect with a direction in which the thermosetting encapsulating sheet penetrates into the gaps, thereby restricting penetration of the thermosetting encapsulating sheet into the gaps.

2. The thermosetting sealing sheet according to claim 1, wherein the non-spherical particles have an average aspect ratio of 1.5 or more.

3. The thermosetting sealing sheet according to claim 1, wherein the non-spherical particles are plate-shaped particles.

4. The thermosetting sealing sheet according to claim 1, wherein the content of the non-spherical particles in the first filler is 1 volume % to 50 volume %.

5. A method for manufacturing a semiconductor device comprising the steps of: preparing a mounting structure comprising a first circuit member and a plurality of second circuit members mounted on the first circuit member, with a gap between the first circuit member and the second circuit member; preparing a thermosetting encapsulating sheet comprising at least a first layer, the first layer being composed of a first thermosetting resin composition, the first thermosetting resin composition including a first filler, and the first filler including non-spherical particles; arranging the thermosetting encapsulating sheet on the mounting structure such that the first layer faces the second circuit member; and sealing the second circuit member by pressing the thermosetting encapsulating sheet against the first circuit member and heating it, wherein an average distance L between the first circuit member and the second circuit member and an average value Dma of maximum diameters Dm of the non-spherical particles satisfy Dma / L≧0.1, a method for manufacturing a sealed body of a mounting structure, the method comprising orienting two or more of the non-spherical particles so that their flat surfaces intersect with a direction of penetration of the thermosetting sealing sheet into the gaps when sealing the mounting structure, thereby restricting penetration of the thermosetting sealing sheet into the gaps.

6. The method for manufacturing a sealing body of a mounting structure according to claim 5, wherein the average aspect ratio of the non-spherical particles is 1.5 or more.

7. The method for manufacturing a sealing body of a mounting structure according to claim 5, wherein the non-spherical particles are plate-shaped particles.

8. The method for manufacturing a sealing body of a mounting structure according to claim 5, wherein the content of said non-spherical particles in said first filler is 1 volume % to 50 volume %.

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