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

Abstract

To prevent a sealant from entering a space when there is a space between a first circuit member and a second circuit member.SOLUTION: A thermosetting sealing sheet 4P is used to seal a mounting structure 10 including a first circuit member 1 and a plurality of second circuit members 2 mounted on the first circuit member, having at least a first layer 41P, 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, 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.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a thermosetting encapsulation sheet and a method for manufacturing an encapsulant of a mounting structure.

Background Art

[0002] Patent Document 1 proposes "a thermosetting resin sheet for encapsulation 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% by mass of the non-conductive filler, and the thermosetting resin sheet for encapsulation is characterized in that it plastically deforms by an external force at room temperature", which is a clay-like thermosetting resin sheet for encapsulation.

[0003] Patent Document 2 proposes "a resin sheet for encapsulation containing a thermosetting resin, a layered silicate compound, and a thermoplastic resin, wherein the thermoplastic resin includes an acrylic resin, the acrylic resin has a carboxyl group, and the acid value of the acrylic resin is 18 or more", which is a resin sheet for encapsulation.

[0004] 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)".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] There may be a gap 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 by utilizing 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, the sealing agent needs to seal the circuit members without filling the above-mentioned gap.

Means for Solving the Problems

[0007] One aspect of the present invention is a thermosetting encapsulation sheet used for encapsulating a mounting structure including at least a first layer, 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 contains non-spherical particles. There is a gap 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 diameter Dm of the non-spherical particles satisfy Dma / L≧0.1. It relates to a thermosetting encapsulation sheet.

[0008] Another aspect of the present invention includes a step of 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; a step of preparing a thermosetting encapsulation sheet including at least a first layer, where the first layer is composed of a first thermosetting resin composition, the first thermosetting resin composition contains a first filler, and the first filler contains non-spherical particles; an arranging step of arranging the thermosetting encapsulation sheet on the mounting structure such that the first layer faces the second circuit member; and a sealing step of pressing and heating the thermosetting encapsulation sheet against the first circuit member to seal 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 diameter Dm of the non-spherical particles satisfy Dma / L≧0.1. It relates to a method for manufacturing a seal body of a mounting structure.

Advantages of the Invention

[0009] The thermosetting encapsulation sheet according to the present disclosure is difficult to penetrate into the space when there is a space between the first circuit member and the second circuit member.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described with 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 can be obtained. In this specification, the description "X is composed of Y" is not limiting, and X may or may not include elements other than Y. That is, the description "X is composed of Y" can be replaced with expressions such as "X includes Y" and "X consists of Y". 50% by mass or more of X may be Y.

[0012] In this specification, the description "X is configured by Y" is not limiting, and X may or may not include elements other than Y. That is, the description "X is configured by Y" can be replaced with expressions such as "X includes Y" and "X consists of Y". 50% by mass or more of X may be Y.

[0013] The present disclosure relates to the following. [Technology 1] Comprising at least a first layer, A thermosetting encapsulation sheet used for encapsulating 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 contains non-spherical particles, A gap is interposed between the first circuit member and the second circuit member, A thermosetting encapsulation sheet in which the average distance L between the first circuit member and the second circuit member and the average value Dma of the maximum diameter Dm of the non-spherical particles satisfy Dma / L≧0.1. [Technology 2] The thermosetting encapsulation sheet according to Technology 1, wherein the average aspect ratio of the non-spherical particles is 1.5 or more. [Technology 3] The thermosetting encapsulation sheet according to Technology 1 or 2, wherein the non-spherical particles are plate-like particles. [Technology 4] The thermosetting encapsulation sheet according to Technology 3, wherein the average thickness of the plate-like particles is 3 μm or less or 1 μm or less. [Technology 5] The thermosetting encapsulation sheet according to any one of Technologies 1 to 4, wherein the content of the first filler contained in the first layer is 35% to 91% by volume. [Technology 6] The thermosetting encapsulation sheet according to any one of Technologies 1 to 5, wherein the first filler further contains first spherical particles. [Technology 7] The thermosetting encapsulation sheet according to Technology 6, wherein the average aspect ratio of the first spherical particles is 1.1 or less. [Technology 8] The thermosetting encapsulation sheet according to Technology 6 or 7, wherein the content of the non-spherical particles contained in the first filler is 1% to 50% by volume. [Technology 9] The thermosetting encapsulation sheet has the 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 contains a second filler, The second filler contains second spherical particles, and is the thermosetting encapsulation sheet according to any one of Technologies 1 to 8. [Technology 10] 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 intervening between the first circuit member and the second circuit members; Preparing a thermosetting encapsulation sheet including at least a first layer, the first layer being composed of a first thermosetting resin composition, the first thermosetting resin composition containing a first filler, and the first filler containing non-spherical particles; An arranging step of arranging the thermosetting encapsulation sheet on the mounting structure such that the first layer faces the second circuit members; An encapsulating step of pressing and heating the thermosetting encapsulation sheet against the first circuit member to encapsulate the second circuit members, wherein an average distance L between the first circuit member and the second circuit members and an average value Dma of a maximum diameter Dm of the non-spherical particles satisfy Dma / L≧0.1. A method for manufacturing an encapsulation body of a mounting structure. [Technology 11] The method for manufacturing an encapsulation body of a mounting structure according to Technology 10, wherein an average aspect ratio of the non-spherical particles is 1.5 or more. [Technology 12] The method for manufacturing an encapsulation body of a mounting structure according to Technology 10 or 11, wherein the non-spherical particles are plate-like particles. [Technology 13] The method for manufacturing an encapsulation body of a mounting structure according to Technology 12, wherein an average thickness of the plate-like particles is 3 μm or less or 1 μm or less. [Technology 14] The method for manufacturing an encapsulation body of a mounting structure according to any one of Technologies 10 to 13, wherein a content ratio of the first filler contained in the first layer is 35% to 91% by volume. [Technology 15] The method for manufacturing an encapsulation body of a mounting structure according to any one of Technologies 10 to 14, wherein the first filler further contains first spherical particles. [Technology 16] The manufacturing method of the encapsulant of the mounting structure according to Technique 15, wherein the average aspect ratio of the first spherical particles is 1.1 or less. [Technique 17] The manufacturing method of the encapsulant of the mounting structure according to Technique 15 or 16, wherein the content of the non-spherical particles contained in the first filler is 1% by volume to 50% by volume. [Technique 18] The thermosetting encapsulation sheet has the 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 contains a second filler. The second filler contains second spherical particles. The manufacturing method of the encapsulant of the mounting structure according to any one of Techniques 10 to 17.

[0014] (Thermosetting encapsulation sheet) The thermosetting encapsulation sheet (hereinafter, also referred to as "thermosetting encapsulation sheet (S)") according to the present disclosure includes at least a first layer. The first layer is composed of a first thermosetting resin composition. The thermosetting encapsulation sheet (S) may have a single-layer structure or a laminated structure of two or more layers. When the thermosetting encapsulation sheet (S) includes only the first layer, the thermosetting encapsulation sheet (S) has a single-layer structure. When the thermosetting encapsulation sheet (S) has a laminated structure of three or more layers, the first layer is preferably disposed on the outermost layer from the viewpoint of enhancing the function of the first layer.

[0015] The first thermosetting resin composition contains a thermosetting resin (hereinafter, also referred to as "first thermosetting resin"). At least a part 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 development of the three-dimensional crosslinked structure is insufficient. When the first layer containing the uncured first thermosetting resin is heated, it becomes a molten first thermosetting resin composition and has fluidity. Thereafter, the curing reaction of the first thermosetting resin proceeds.

[0016] The thermosetting encapsulation sheet (S) is used, for example, as an encapsulant for circuit members such as electronic components. The thermosetting encapsulation sheet (S) may 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 (for example, electronic components) mounted on the first circuit member.

[0017] The first thermosetting resin composition contains a first filler, and the first filler contains non-spherical particles. Non-spherical particles widely include particles having a shape other than spherical. When there is a gap between the first circuit member and the second circuit member and the mounting structure is encapsulated by the thermosetting encapsulation sheet (S) while maintaining the gap, the first layer containing non-spherical particles acts effectively.

[0018] In the case of spherical particles, since there is no directionality (anisotropy) in the particles, they do not have the property of being oriented in one direction by an external force. On the other hand, in the case of non-spherical particles, when an external force is applied, they have the property (anisotropy) of being oriented in one direction according to the particle shape. When the thermosetting encapsulation 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, when the non-spherical particles have a flat surface, the fluidity of the first thermosetting resin composition is increased in the direction in which the flat surface of the non-spherical particles is oriented, and the fluidity of the first thermosetting resin composition in other directions is decreased. By such an action, when there is a gap between the first circuit member and the second circuit member, the intrusion of the molten first thermosetting resin composition into the gap is restricted.

[0019] 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 having such a large aspect ratio are considered to be particularly likely to be oriented in the molten first thermosetting resin composition. The aspect ratio R of the non-spherical particles refers to the ratio of the maximum diameter Dm of the non-spherical particles to the maximum dimension of the non-spherical particles in the 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 by the method using a scanning electron microscope (SEM) described below. Also, 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.

[0020] The non-spherical particles may be plate-like particles. The plate-like shape may be any flat shape, for example, scaly or flaky.

[0021] The average thickness of the plate-like particles may be 3 μm or less, or 1 μm or less. Such thin plate-like particles are considered to be particularly likely to be oriented in the molten first thermosetting resin composition. The thickness of the plate-like particles refers to the maximum dimension in the direction perpendicular to either one of the two flat surfaces of the plate-like particles. The average thickness of the plate-like particles may be determined as the average value of the thicknesses of 10 plate-like particles by the method using a scanning electron microscope (SEM) described below.

[0022] 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 having such a large aspect ratio are considered to be particularly likely to be oriented in the molten first thermosetting resin composition. 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 obtained as the average value of the aspect ratios R of 10 plate-like particles by the method using the following SEM image. Also, the average maximum diameter Dma of the plate-like particles may be obtained 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 particles in the direction perpendicular to the maximum diameter Dm of the particles (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 also be 1 μm to 30 μm.

[0023] Hereinafter, the method for obtaining the maximum diameter Dma and the average aspect ratio Ra of the non-spherical particles (or plate-like particles) will be described. For example, Dma and Ra can be obtained by performing the following operations (1) to (5) in order of number.

[0024] (1) Prepare a cured product of the thermosetting encapsulation sheet (S). The cured product of the thermosetting encapsulation sheet (S) can be obtained by curing the thermosetting encapsulation sheet (S) at 150 °C for 1 hour or more. Also, as the cured product, a portion of the encapsulant of the encapsulated structure encapsulated with the thermosetting encapsulation sheet (S) may be used. The encapsulant may be a commercially available product. Note that the curing conditions are not particularly limited as long as a cured product capable of obtaining a cross-section described later can be obtained.

[0025] (2) Cut the cured product or the encapsulant parallel to the thickness direction of the thermosetting encapsulation sheet (S) (or the stacking direction of the first circuit member and the second circuit member in the encapsulant), and polish the cross-section with a polishing device. In the cross-section of the encapsulant, the first circuit member, the second circuit member, and the gap between them can be observed.

[0026] (3) Observe the polished surface under a scanning electron microscope (SEM) at a magnification of 2000 times. As an example, the observation may be performed at three locations on the polished surface, that is, in three fields of view.

[0027] (4) The larger the size of the non-spherical particles, the greater the impact on the fluidity of the molten first thermosetting resin composition. Therefore, in one field-of-view image (SEM image), select 10 particles (the top 10 in terms of the maximum diameter Dm) in descending order from the particle with the largest maximum diameter Dm, and obtain the outer peripheral shape of these particles. For example, the top 10 in terms of the maximum diameter Dm may be automatically selected using image processing software or the like.

[0028] (5) From the outer peripheral shape, use image processing software or the like to determine the maximum diameter Dm of each particle and the maximum dimension Dw of the particle in the direction perpendicular to the maximum diameter Dm, and calculate the aspect ratio R (= Dm / Dw). Calculate the average value of the maximum diameters Dm of 10 (10×N when measured in N fields of view) particles as Dma, and calculate the average value of the aspect ratios R of the 10 (or 10×N) particles as the average aspect ratio Ra.

[0029] The non-spherical particles may be polyhedral particles. That is, non-spherical may mean polyhedral. The number of faces of the polyhedron is, for example, 4 to 19, or may be 4 to 15. Polyhedral means, for example, tetrahedral, cubic (hexahedral), octahedral, decahedral, dodecahedral, etc.

[0030] 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 obtained as the average value of the maximum diameters Dm of 10 polyhedral particles by the method using the aforementioned SEM image.

[0031] The average aspect ratio of the polyhedral particles may be, for example, 1.5 or more, or may be 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 the direction perpendicular to the maximum diameter Dm. The average aspect ratio of the polyhedral particles may be obtained as the average value of the aspect ratios of 10 polyhedral particles by the method using the SEM image described above.

[0032] The non-spherical particles may be acicular particles. Note that the acicular particles include rod-shaped particles and short fiber-shaped particles.

[0033] 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 obtained as the average value of the lengths of 10 acicular particles by the method using the SEM image described above. Note that 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 obtained as the average value of the thicknesses of 10 acicular particles by the method using the SEM image described above.

[0034] When the first particle is an acicular particle, the average aspect ratio of the acicular particles may be 1.5 or more, may be 3 or more, may be 4 or more, or may be 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 obtained as the average value of the aspect ratios of 10 acicular particles by the method using the SEM image described above.

[0035] Note that the amount of polyhedral particles or acicular particles used may be increased compared to plate-shaped particles. In that case, it becomes easier to control the intrusion of the sealing material into the space between the first circuit member and the second circuit member.

[0036] When there is a gap between the first circuit member and the second circuit member, for example, when bumps are 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 diameter Dm of the non-spherical particles need to satisfy Dma / L≥0.1, and it is preferable to satisfy Dma / L≥0.2. In this case, the intrusion of the molten first thermosetting resin composition into the gap is significantly restricted. The average distance L can be measured in a plane parallel to the lamination direction of the first circuit member and the second circuit member, in a cross section obtained by simultaneously cutting the first circuit member and the second circuit member. In the said cross section, the separation distance between the first circuit member and the second circuit member is measured at a plurality of cross sections (5 cross sections or more), and their average value may be taken as L. However, the separation distance shall be the shortest distance between the edge of the outer periphery of the second circuit member and the first circuit member.

[0037] 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.

[0038] The inorganic materials can be metals such as gold, silver, copper, nickel, metal oxides (such as silicon oxide (especially silica), aluminum oxide, titanium oxide, calcium oxide, magnesium oxide, etc.), metal carbonates (such as calcium carbonate, magnesium carbonate, etc.), metal hydroxides (such as aluminum hydroxide, magnesium hydroxide, etc.), metal silicates (such as calcium silicate, magnesium silicate, etc.), metal nitrides (such as boron nitride, aluminum nitride, etc.), metal carbides (such as silicon carbide, etc.), talc, mica, kaolin, etc. However, the inorganic materials are not limited to these.

[0039] The organic materials can be resins such as polystyrene, polyolefin, polyester, cellulose, polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyamide, polyphenylene ether, polyparaphenylene benzobisoxazole, polybutylene terephthalate, polyacetal, liquid crystal polymer, etc. However, the organic materials are not limited to these.

[0040] The volume content ratio of the first filler contained in the first layer is, for example, 35% by volume to 91% by volume, preferably 45% by volume to 83% by volume, and more preferably 56% by volume to 76% by volume. The volume content ratio 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 Thus, the mass content ratio 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.

[0041] The volume content ratio of the non-spherical particles contained in the first filler may be 100% by volume, but a part of the first filler may be spherical particles (first spherical particles). When the first filler further contains the first spherical particles, the volume content ratio Cns of the non-spherical particles contained in the first filler is 1% by volume to 50% by volume, and the volume content ratio Cs of the first spherical particles contained in the first filler may be 50% by volume to 99% by volume. From the viewpoint of enhancing the fluidity of the first thermosetting resin composition (fluidity other than the gap between the first circuit member and the second circuit member), it is preferable that the volume content ratio Cns of the non-spherical particles and the volume content ratio Cs of the first spherical particles satisfy Cns ≦ Cs, and it may also satisfy 1.5 ≦ Cs / Cns.

[0042] The volume content ratio of the first filler contained in the first layer may be determined from the SEM image of the polished surface of the cured product or the encapsulant described above. The area of the field of view of the SEM image can be distinguished into the area Sf occupied by the cross-section of the filler and the area Sr occupied by the cross-section other than the filler (resin component). The ratio of the area Sf in the total of the area Sf and the cross-section Sr can be regarded as the volume content ratio of the first filler contained in the first layer.

[0043] In addition, the volume content ratio of the non-spherical particles contained in the first filler may be determined from the SEM image of the polished surface of the cured product or the sealing body described above. The area Sf can be distinguished into the area Sfns occupied by the cross-section of the non-spherical particles and the area Sfs occupied by the cross-section of the first spherical particles. The ratio of the area Sfns in the total of the area Sfns and the cross-section Sfs can be regarded as the volume content ratio of the non-spherical particles contained in the first filler.

[0044] The first spherical particles do not necessarily have to be true spherical particles, and any particles in which most of the particle surface is composed of a curved surface are acceptable. There may be minute irregularities on the curved surface of the particle surface. For example, they may be ellipsoidal. Polyhedral particles with 20 or more faces may be regarded as the first spherical particles.

[0045] The average particle diameter Da of the first spherical particles may be 0.05 μm to 100 μm, or may be 0.1 μm to 30 μm. The particle diameter of the first spherical particles refers to the maximum diameter of the first spherical particles. The average particle diameter Da of the first spherical particles may be obtained as the average value of the maximum diameters of 100 first spherical particles in accordance with the method using the SEM image described above, similar to Dma.

[0046] The average aspect ratio of the first spherical particles may be, for example, 1.2 or less, or may be 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 is the maximum dimension of the particle in the direction perpendicular to the maximum diameter of the particle. The average aspect ratio of the first spherical particles may be obtained as the average value of the aspect ratios of 100 first spherical particles in accordance with the method using the SEM image described above, similar to the average aspect ratio Ra.

[0047] The ratio (Dma / Da) of the average value Dma of the maximum diameter Dm of the non-spherical particles to the average particle diameter Da of the first spherical particles preferably satisfies 0.01 to 1000, and more preferably satisfies 0.01 to 100.

[0048] In addition, when 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 by a laser diffraction / scattering particle size distribution measuring device is preferably 1 μm to 30 μm.

[0049] Further, 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 by a laser diffraction / scattering particle size distribution measuring device is preferably 0.1 μm to 30 μm.

[0050] The ratio (D50A / D50B) of the mode diameter D50A to the mode diameter D50B preferably satisfies 0.01 to 1000, more preferably satisfies 0.01 to 100. Further, Dma / D50B may satisfy 0.01 to 1000, and more preferably 0.01 to 100, and D50A / Da may satisfy 0.01 to 1000, and more preferably 0.01 to 100.

[0051] 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, an inorganic material is preferable, and examples include 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.

[0052] The thermosetting encapsulation 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 contains a thermosetting resin (hereinafter also referred to as "second thermosetting resin"). At least a part 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 development of the three-dimensional crosslinked structure is insufficient. When the uncured second layer is heated, it becomes a molten state and has fluidity. 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.

[0053] The second thermosetting resin composition contains a second filler, and the second filler contains 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.

[0054] The thickness T1 of the first layer only needs to have a sufficient thickness to limit the intrusion of the encapsulant into the space between the first circuit member and the second circuit member, and is preferably greater than the average distance L between the first circuit member and the second circuit member (for example, T1 > 1.1L). The thickness T1 of the first layer is, for example, 20 μm to 300 μm, and may also be 40 μm to 240 μm.

[0055] The total thickness of T1 and T2 is, for example, 40 μm ≤ T1 + T2 ≤ 500 μm, and may also be 50 μm ≤ T1 + T2 ≤ 350 μm, or even 100 μm ≤ T1 + T2 ≤ 300 μm.

[0056] The compositions of the first and second thermosetting resin compositions are not particularly limited except for having the configurations described above. The first and second thermosetting resins are not particularly limited, but each independently, an epoxy resin, a (meth)acrylic resin, a phenol 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, etc. can be used. These may be used alone or in combination of two or more. Among them, an epoxy resin is preferred.

[0057] The epoxy resin is not particularly limited, and for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, phenol novolac type epoxy resin, naphthalene type epoxy resin, alicyclic aliphatic epoxy resin, glycidyl ether of organic carboxylic acids, etc. can be used. 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 and another polymer such as a polyether-modified epoxy resin or a silicone-modified epoxy resin. Among them, bisphenol AD type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin and / or bisphenol F type epoxy resin are preferred. In particular, bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferred in terms of excellent heat resistance and water resistance and low cost.

[0058] For viscosity adjustment of the first and second thermosetting resin compositions, the epoxy resin can contain a monofunctional epoxy resin having one epoxy group in the molecule in an amount of about 0.1 to 30% by mass based on the total epoxy resin. As such a monofunctional epoxy resin, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, ethyl diethylene glycol glycidyl ether, dicyclopentadiene glycidyl ether, 2-hydroxyethyl glycidyl ether, etc. can be used. These may be used alone or in combination of two or more.

[0059] The first and second thermosetting resin compositions contain a curing agent. The curing agent is not particularly limited, and examples thereof include phenolic curing agents (such as phenolic resins), dicyandiamide-based curing agents (such as dicyandiamide), urea-based curing agents, organic acid hydrazide-based curing agents, polyamine salt-based curing agents, amine adduct-based curing agents, acid anhydride-based curing agents, imidazole-based curing agents, amine-based curing agents, active ester-based curing agents, benzoxazine-based curing agents, maleimide-based curing agents, and the like. These may be used alone or in combination of two or more. The type of curing agent is appropriately selected according to the thermosetting resin. Among them, from the viewpoints of low outgassing property, moisture resistance, heat cycle resistance, etc. during curing, it is preferable to use a phenolic curing agent.

[0060] The amount of the curing agent varies depending on the type of the curing agent. When using an epoxy resin, for example, it is preferable to use a curing agent in an amount such that the equivalent number of functional groups of the curing agent is 0.001 to 2 equivalents, and further 0.005 to 1.5 equivalents, per equivalent of epoxy groups.

[0061] Note that dicyandiamide-based curing agents, urea-based curing agents, organic acid hydrazide-based curing agents, polyamine salt-based curing agents, and amine adduct-based curing agents are latent curing agents. The activation temperature of the latent curing agent is preferably 60°C or higher, and further preferably 80°C or higher. Also, the activation temperature is preferably 250°C or lower, and further preferably 180°C or lower. Thereby, a resin composition that cures rapidly at a temperature above the activation temperature can be obtained.

[0062] The first and second thermosetting resin compositions may contain a thermoplastic resin. The thermoplastic resin may have an effect of assisting the thermosetting encapsulation sheet (S) having the first layer and the thermosetting encapsulation sheet (S) having the first layer and the second layer to maintain the sheet form. That is, the thermoplastic resin can be blended as a sheeting agent for the thermosetting resin composition. By sheeting the thermosetting resin composition, the handleability in the encapsulation process is improved.

[0063] Examples of the types of thermoplastic resins include acrylic resins, phenoxy resins, polyolefins, polyurethanes, block isocyanates, polyethers, polyesters, polyimides, polyvinyl alcohol, butyral resins, polyamides, vinyl chloride, celluloses, thermoplastic epoxy resins, thermoplastic phenol resins, and the like. Among them, acrylic resins are preferred in terms of excellent function as a sheeting agent. 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.

[0064] 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 diameter of 0.01 to 200 μm, preferably 0.01 to 100 μm. The above particles may have a core-shell structure. In this case, the core may be, for example, a polymer containing units derived from at least one monomer selected from the group consisting of n-, i-, and t-butyl (meth)acrylate, or a polymer containing units derived from other (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, (meth)acrylic acid, etc. and a polyfunctional monomer such as 1,6-hexanediol diacrylate.

[0065] The first and second thermosetting resin compositions may contain a third component other than the above. Examples of the third component include a curing accelerator, a polymerization initiator, an ion catcher, a flame retardant, a pigment, a silane coupling agent, a thixotropy-imparting agent, and the like.

[0066] FIG. 1 is a cross-sectional view schematically showing 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 for sealing the second circuit members 2. A gap S is formed between the first circuit member 1 and the second circuit member 2.

[0067] The sealing material 4 is a cured product of a thermosetting sealing sheet having a two-layer structure including a first layer and a second layer laminated on the first layer. The sealing material 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 sealing material 4 seals the second circuit member 2 while maintaining the gap S.

[0068] In this embodiment, the second circuit member 2 is mounted on the first circuit member 1 via the bumps 3, but the mounting method of the second circuit member 2 on the first circuit member 1 is not limited to this.

[0069] FIG. 2 is an enlarged view of a part 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 having a flat shape have two flat surfaces facing each other and have anisotropy of orienting 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.

[0070] When the molten first thermosetting resin composition receives an external force necessary 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 part of the gap S. Also, the plate-like particles reduce the fluidity of the first thermosetting resin composition in a direction intersecting the direction in which the flat surfaces are oriented. Therefore, the molten first thermosetting resin composition is less likely to enter the gap S between the first circuit member and the second circuit member.

[0071] FIG. 3 is a cross-sectional view schematically showing the structure of a thermosetting sealing sheet (S) 4P having a two-layer structure including a first layer 41P and a second layer 42P. In the sealing process, the thermosetting sealing sheet (S) 4P is arranged such that the first layer 41P contacts the second circuit member 2. Therefore, except for the facing surface of the second circuit member 2 with the first circuit member 1, it is covered with the cured product 41 of the first layer.

[0072] The manufacturing method of the thermosetting encapsulation sheet (S) 4P having the first layer 41P and the second layer 42P (hereinafter also referred to as "laminated sheet 4P") is not particularly limited. The laminated sheet 4P may be formed by a lamination method in which each layer is separately manufactured and then laminated, or may be formed by a coating method in which the materials of each layer are sequentially coated.

[0073] 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 solvent-free paste not containing a solvent (hereinafter simply referred to as "paste"), respectively, and a layer forming step of forming each layer from each paste. The layer forming step is not particularly limited, but for example, each paste may be applied on a film and dried, or the heat-cured resin composition melt-kneaded may be molded into a specified thickness by a hot press or a rolling roll. After forming the first layer 41P and the second layer 42P by such a method, they are laminated in this order. At that time, when the paste contains a thermoplastic resin as a sheet-forming agent, the sheet-forming agent may be gelled. Gelation (sheet formation) may be performed by heating the thin film at a temperature lower than the curing temperature of the first or second thermosetting resin composition (for example, 70 to 150 ° C) for 1 to 10 minutes after thinning the paste.

[0074] In the coating method, after forming the first layer 41P by the above method, for example, a paste containing a second thermosetting resin composition is coated on the surface of the first layer 41P to form the second layer 42P. When the paste contains a thermoplastic resin as a sheet-forming agent, the sheet-forming agent may be gelled. Gelation may be sequentially performed after forming each thin film from each paste, or may be performed after forming a laminate of thin films.

[0075] Each layer (thin film) can be formed using, for example, a die coater, a roll coater, a doctor blade, or the like. In this case, it is preferable to adjust the viscosity of the paste to be 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 thereafter.

[0076] FIG. 4 is an explanatory diagram schematically showing a method for manufacturing a mounting structure according to an embodiment (hereinafter also referred to as "manufacturing method (M)"). The manufacturing method (M) includes a first preparation step, a second preparation step, an arrangement step, and a sealing step. After the sealing step, a singulation step may be performed.

[0077] (First Preparation Step) The first preparation step is a step of preparing a mounting structure before sealing. The mounting structure before sealing includes a first circuit member 1 and a plurality of second circuit members 2 mounted on the first circuit member 1, and a gap S is interposed between the first circuit member 1 and the second circuit member 2. The height of the gap S generally corresponds to the height of the bump 3.

[0078] The first circuit member 1 can be, for example, a semiconductor element, a semiconductor package, a glass substrate, a resin substrate, a ceramic substrate, a silicon substrate, or the like. 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 the resin substrate include an epoxy resin substrate (e.g., a glass epoxy substrate), a bismaleimide triazine substrate, a polyimide resin substrate, and a fluororesin substrate. The first circuit member 1 may be a component-embedded substrate having a semiconductor chip or the like inside.

[0079] The second circuit member 2 is mounted on the first circuit member 1 via, for example, bumps 3. Thereby, a gap S is formed 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 vibrator chip, a crystal oscillator chip, a MEMS device, an RFIC, and a SAW filter.

[0080] The bump 3 has conductivity, and the first circuit member 1 and the second circuit member 2 are electrically connected via the bump 3. The height of the bump 3 is not particularly limited, and for example, it may be 5 μm to 150 μm. The material of the bump 3 is not particularly limited as long as it has conductivity, and examples thereof include copper, gold, solder, and the like.

[0081] That is, the mounting structure may have a chip - on - board (CoB) structure (including chip - on - wafer (CoW), chip - on - film (CoF), chip - on - glass (CoG)) in which the second circuit member 2 is mounted on the first circuit member 1, a chip - on - chip (CoC) structure, a chip - on - package (CoP) structure, and a package - on - package (PoP) structure, etc. The mounting structure may be a multilayer mounting structure in which the first circuit member 1 and / or the second circuit member 2 are further laminated on the first circuit member 1 on which the second circuit member 2 is mounted.

[0082] (Second Preparation Step) The second preparation step is a step of preparing a thermosetting encapsulation sheet (S) 4P. The thermosetting encapsulation sheet (S) 4P may include at least a first layer 41P. The first layer 41P is composed of a first thermosetting resin composition.

[0083] The thermosetting encapsulation sheet (S) 4P may have a second layer 42P laminated on the first layer 41P. The second layer 42P is composed of a second thermosetting resin composition.

[0084] (Arrangement Step) The arrangement step is a step of arranging the thermosetting encapsulation sheet (S) 4P on the mounting structure (Fig. 3(a)). In the arrangement step, for example, the thermosetting encapsulation sheet (S) 4P is arranged on the mounting structure so that the second circuit member 2 is covered by the thermosetting encapsulation sheet (S) 4P. At this time, the first layer 41P is opposed to the second circuit member 2.

[0085] (Encapsulation Step) The sealing process is a process of pressing the thermosetting sealing sheet (S) 4P against the first circuit member 1 and heating and curing it to seal the second circuit member 2 (Figs. 4(b) and (c)). When the first layer 41P faces the second circuit member 2, the second circuit member 2 is sealed while maintaining the gap S.

[0086] The pressing of the thermosetting sealing sheet (S) 4P against the first circuit member 1 may be a hot press process (compression molding process). The hot press process is performed, for example, while heating the thermosetting sealing sheet (S) 4P at a temperature lower than the curing temperature of the first (and second) thermosetting resin composition contained in the thermosetting sealing sheet (S) 4P. By hot pressing, the first layer 41P is brought into close contact with the surface of the second circuit member 2, and the first layer is stretched between the second circuit members 2 until it reaches the surface of the first circuit member 1, which may enhance the reliability of the sealing of the second circuit member 2.

[0087] The hot press process may be performed 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 appropriately set according to the pressing method and the composition of the thermosetting resin composition. The above heating is performed, for example, at 40 to 200 °C (preferably 50 to 180 °C) for 1 second to 300 minutes (preferably 3 seconds to 300 minutes).

[0088] Subsequently, the molten thermosetting resin composition is heated at the curing temperature to cure the thermosetting resin composition and form the sealing material 4. Thereby, the second circuit member 2 is sealed. The curing conditions of the thermosetting resin composition may be appropriately set according to the composition of the thermosetting resin composition. The curing of the thermosetting resin composition is performed, for example, at 50 to 200 °C (preferably 120 to 180 °C) for 1 second to 300 minutes (preferably 60 minutes to 300 minutes).

[0089] The thermal pressing process and the curing of the thermosetting resin composition may be carried out separately or simultaneously. For example, in a reduced-pressure atmosphere, the thermosetting resin composition contained in the thermosetting encapsulation sheet (S) 4P is thermally pressed at a temperature lower than the curing temperature, and then the reduced pressure is released, and it is further heated at a higher temperature under atmospheric pressure to cure the thermosetting resin composition. Alternatively, under atmospheric pressure, after thermally pressing at a temperature lower than the curing temperature of the thermosetting resin composition contained in the thermosetting encapsulation sheet (S) 4P, it may be further heated at a higher temperature to cure the thermosetting resin composition. Also, by thermally pressing at the curing temperature in a reduced-pressure atmosphere, the thermosetting resin composition may be cured during the reduced pressure.

[0090] (Dicing process) The obtained mounting structure 10 may be subjected to a dicing process of dicing each second circuit member 2 (Fig. 4(d)). Thereby, a chip-level mounting structure (mounted chip 20) is obtained. Also, a dicing process may be performed such that a plurality of second circuit members 2 are included in one package. Thereby, a mounting structure on which a plurality of chips such as a multi-chip package or a module are mounted is obtained.

[0091] Next, the manufacturing method of the thermosetting encapsulation sheet and the mounting structure according to the present invention will be described in more detail based on examples, but the following examples do not limit the present invention.

[0092] <<Example 1>> (Preparation of thermosetting resin composition) The components shown below were blended in the compositions described in Table 1 to prepare the 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 type epoxy resin, 60 parts by mass of phenol novolak 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) are blended.

[0093] Also, the physical properties of the filler are shown in Table 2.

[0094]

Table 1

[0095]

Table 2

[0096] (Preparation of thermosetting sheet (S)) Next, a first resin composition and a second resin composition each containing methyl ethyl ketone as a solvent were sequentially coated on a release film at a predetermined thickness shown in Table 3, and molded by a coating method in which the solvent was volatilized by drying to prepare thermosetting encapsulation sheets B1 and A1 to A22 having a two-layer structure including a first layer and a second layer.

[0097]

Table 3A

Table 3B

[0098] (Fabrication of evaluation mounting structure) Next, 16 dummy chips of the same size (second circuit member, 1 mm × 1 mm, height 0.2 mm) were arranged at equal intervals of 4 vertically × 4 horizontally = 16 on a glass substrate (first circuit member, 50 mm square, thickness 1 mm) via bumps. The interval between the chips was 300 μm, and the chip arrangement was 4 columns × 4 rows. A predetermined interval (L) shown in Table 3 was provided between the chip and the substrate by a predetermined bump.

[0099] (Encapsulation of evaluation mounting structure) Each thermosetting encapsulation sheet was used to encapsulate the evaluation mounting structure by compression molding. Specifically, in a reduced-pressure atmosphere of 2 hPa, the thermosetting encapsulation sheet was placed on the mounting structure such that the first layer faced the chip (second circuit member), and the second circuit member was encapsulated by heating at 100°C while pressing the thermosetting encapsulation sheet against the first circuit member at 0.7 MPa, and then heating in a hot air oven at 150°C for 1 hour to cure.

[0100] The penetration distance of the encapsulant that penetrated between the chip and the substrate from the edge of each chip (the maximum reach point of the encapsulant from the edge of each chip) was measured. Table 3 shows the following evaluations. The penetration distance in the following evaluations is the average value for 16 chips, and the penetration distance variation is the difference between the penetration distance of the chip with the maximum penetration distance and the penetration distance of the chip with the minimum penetration distance among the 16 chips.

[0101] (Penetration distance) ◎... 0 μm or more and 20 μm or less 〇... More than 20 μm and 35 μm or less △... More than 35 μm and 50 μm or less ×... More than 50 μm

[0102] (Penetration distance variation) ◎... 0 μm or more and 15 μm or less 〇... More than 15 μm and 20 μm or less ×... More than 20 μm

[0103] When the thermosetting encapsulation sheets A1 to A22 of the examples were used, the penetration distance was smaller than when the thermosetting encapsulation sheet B1 of the comparative example was used. This is considered to be the effect of using non-spherical particles as part of the first filler. Actually, when observing the cross-section of the encapsulated evaluation mounting structure, it was confirmed that the flat surfaces of the non-spherical particles were oriented so as to intersect the penetration direction of the encapsulant.

Industrial Applicability

[0104] The present invention is suitable for the field of encapsulation of mounting structures. According to the thermosetting encapsulation sheet according to the present invention, the penetration of the encapsulant into the space between the circuit member and the substrate can be suppressed.

Explanation of Signs

[0105] 10: Mounting structure 1: First circuit member 2: Second circuit member 3: Bump 4: Sealing agent (cured product of thermosetting sealing sheet) 4P: Sheet 41P: First layer 42P: Second layer 20: Mounted chip

Claims

1. comprising at least a first layer, a thermosetting encapsulation sheet used for encapsulating a mounting structure comprising 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 contains non-spherical particles, a gap is interposed between the first circuit member and the second circuit member, a thermosetting encapsulation sheet, wherein an average distance L between the first circuit member and the second circuit member and an average value Dma of a maximum diameter Dm of the non-spherical particles satisfy Dma / L≥0.

1.

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

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

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

5. a step of 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 interposed between the first circuit member and the second circuit member; a step of preparing a thermosetting encapsulation sheet comprising at least a first layer, the first layer being composed of a first thermosetting resin composition, the first thermosetting resin composition containing a first filler, and the first filler containing non-spherical particles; an arranging step of arranging the thermosetting encapsulation sheet on the mounting structure such that the first layer faces the second circuit member; and a sealing step of pressing and heating the thermosetting encapsulation sheet against the first circuit member to seal the second circuit member. A method for manufacturing a sealing body of a mounting structure, wherein the average distance L between the first circuit member and the second circuit member and the average value Dma of the maximum diameter Dm of the non-spherical particles satisfy Dma / L≥0.

1.

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-like particles.

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

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