Encapsulating sheet and system board for system board on which the processor is mounted.

Abstract

The present invention provides a sealing material sheet that can improve adhesion to a functional layer even when a functional layer is laminated on the surface of the sealing material sheet. [Solution] The sealing material sheet 1 for a system board on which a processor is mounted has a multilayer structure comprising a core layer 11 and a skin layer 12a, wherein the core layer 11 contains polyethylene resin as the base resin and the skin layer 12a contains polypropylene resin as the base resin.

Description

[Technical Field]

[0001] The present invention relates to a sealing sheet for a system board on which a processor is mounted, and to a system board. [Background technology]

[0002] System boards equipped with processors that transmit electrical signals for controlling various devices have been widely used in a variety of fields.

[0003] Furthermore, in miniaturized electronic devices commonly known as "smartphones" and "tablets," there is an increasing demand to implement numerous electronic circuit devices in a limited space and to arrange these electronic circuit devices in an even more compact configuration.

[0004] Furthermore, miniaturized electronic devices have disadvantages because many circuits are integrated into a small space. For example, electromagnetic interference can occur due to electromagnetic waves generated by the electronic device itself, entering the device from the outside, or flowing through the connected circuit wiring. In addition, heat is inevitably generated due to the electrical resistance that occurs at the connections of each component when the device is in operation.

[0005] For example, Patent Document 1 describes a technology relating to an electronic circuit board assembly comprising an electronic circuit board, an electronic circuit device, an electromagnetic interference shielding structure (electromagnetic reflection shield), and a heat dissipation pad.

[0006] Patent Document 1 describes that this electromagnetic interference shielding structure and heat dissipation pad for the electronic circuit board assembly can be attached to the electronic circuit board at low cost and with ease, and that by using the electromagnetic interference shield and a single heat dissipation pad, the electronic circuit board assembly can be made extremely thin.

[0007] Thus, the encapsulating sheet for the system board on which the processor is mounted may be equipped with functional layers such as an electromagnetic interference shielding structure to suppress electromagnetic interference and a heat dissipation pad to dissipate heat from the processor. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2017-536693 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Now, the encapsulating sheet for the system board on which the processor is mounted is laminated onto the board, covering the processor. As a result, the encapsulating sheet conforms to the shape of the processor, which can cause irregularities on the surface of the encapsulating sheet on the side opposite the board.

[0010] Our research has revealed that even when a functional layer is laminated onto the surface of the encapsulating material sheet on the opposite side of the substrate, a partial gap is created between the encapsulating material sheet and the functional layer, making it impossible to improve adhesion to the functional layer.

[0011] The present invention aims to provide a sealing material sheet that can improve adhesion to a functional layer even when a functional layer is laminated on the surface of the sealing material sheet. [Means for solving the problem]

[0012] The inventors have found that the above problems can be solved by the following configuration, This invention has now been completed. Specifically, the present invention provides the following:

[0013] (1) A sealing sheet for a system board on which a processor is mounted, It has a multilayer structure consisting of a core layer and a skin layer. The core layer contains a polyethylene-based resin as a base resin, and has a Vicat softening point in the range of 30°C or higher and 100°C or lower. Sealing material sheet.

[0014] (2) The surface roughness Ra of the skin layer is 15 μm or less. The sealing material sheet according to (1).

[0015] (3) A system substrate including a processor, a substrate, a processor disposed on the surface of the substrate, and the sealing material sheet according to (1) or (2), and is provided with The sealing material sheet covers the processor and is laminated on the substrate such that the core layer is located closer to the substrate side than the skin layer. System substrate.

[0016] (4) A functional layer is provided on the surface of the skin layer of the sealing material sheet. The system substrate according to (3).

Advantages of the Invention

[0017] For the sealing material sheet for a system substrate on which a processor of the present invention is mounted, the adhesion to the functional layer can be enhanced even when a functional layer is laminated on the surface of the sealing material sheet on the side opposite to the substrate.

Brief Description of the Drawings

[0018] [Figure 1] It is a cross-sectional view schematically showing the layer structure of the sealing material sheet of an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of the layer structure of the sealing material sheet of an embodiment of the present invention and a system substrate on which a processor is mounted.

Modes for Carrying Out the Invention

[0019] The following describes specific embodiments of the present invention in detail. However, the present invention is not limited in any way to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0020] ≪1. Sealing Sheet≫ The sealing sheet according to this embodiment is a sealing sheet for a system board on which a processor is mounted. Specifically, it is a resin sheet that can be used as a sealing sheet to cover and laminate various components such as a processor, which are placed and mounted on the board of a system board, in order to protect them from physical impact.

[0021] Furthermore, the sealing sheet according to this embodiment has a multilayer structure comprising a core layer and a skin layer, wherein the core layer contains a polyethylene-based resin as the base resin, and the skin layer contains a polypropylene-based resin as the base resin.

[0022] In this specification, the term "polyethylene resin," etc., is used to include not only "polyethylene resin" but also copolymers that contain, for example, 50% or more (preferably 70% or more, more preferably 80% or more) polyethylene main chains, and in which a portion of the main chains is replaced by other main chains different from polyethylene.

[0023] A sealing sheet can be made that has a skin layer containing such a polypropylene resin, and a functional layer on the surface of this skin layer, thereby improving adhesion to the functional layer.

[0024] Furthermore, by laminating the skin layer and the functional layer via an adhesive layer, the functional layer can be given even greater release properties. This makes it possible to peel off the functional layer relatively easily without damaging the functional layer or the sealing sheet, thereby promoting the reattachment of the functional layer to the sealing sheet during system substrate manufacturing and facilitating the reuse (recycling) of the functional layer.

[0025] Furthermore, by incorporating a core layer containing polyethylene resin, it becomes possible to provide a desirable level of molding properties for use as a sealing material sheet for system substrates.

[0026] Furthermore, the sealing sheet according to this embodiment may be a two-layer film comprising a core layer containing polyethylene resin and a skin layer (first skin layer) containing polypropylene resin, but it may also be a three-layer structure as shown in Figure 1. Specifically, a first skin layer 12a containing polypropylene resin may be provided on one side of the core layer 11, and a second skin layer 12b may be provided on the other side of the core layer 11. In this specification, for convenience, the skin layer located on the side where the functional layer is laminated (opposite the substrate, hereinafter also referred to as the functional layer lamination side) may be referred to as the first skin layer, and the skin layer located on the substrate side (hereinafter also referred to as the substrate lamination side) may be referred to as the second skin layer.

[0027] When a second skin layer 12b, which is arranged on the substrate side, is laminated onto the sealing sheet 1 according to this embodiment, it is preferable that the second skin layer 12b contains a polyethylene-based resin as its base resin, similar to the core layer 11. Specifically, it is preferable to place the layer with a lower MFR in the center as the core layer 11, and the layer with a higher MFR on the substrate side as the second skin layer 12b. Even when the sealing sheet 1 according to this embodiment does not have the second skin layer 12b, it still has sufficiently good molding properties. However, by placing the layer with a relatively high MFR as the second skin layer 12b, the sealing sheet can be made to have improved molding properties while also improving adhesion to other laminated members such as substrates and processors.

[0028] Furthermore, when a second skin layer 12b is laminated on the substrate side of the sealing material sheet 1 according to this embodiment, it is preferable to include a silane copolymer (silane-modified resin) as part of the base resin. This further enhances adhesion to other laminated components such as substrates and processors.

[0029] The Vicat softening point of the sealing sheet 1 (the Vicat softening point measured from the side where the substrate is placed) is not particularly limited, but is preferably 30°C or higher and 100°C or lower, more preferably 35°C or higher and 95°C or lower, and even more preferably 40°C or higher and 90°C or lower. The lower limit of the Vicat softening point of the sealing sheet 1 is preferably 30°C or higher, more preferably 35°C or higher, and even more preferably 40°C or higher. The upper limit of the Vicat softening point of the sealing sheet 1 is preferably 100°C or lower, more preferably 95°C or lower, and even more preferably 90°C or lower.

[0030] The thickness (total thickness) of the sealing material sheet 1 according to this embodiment is not particularly limited and varies depending on the type of equipment used, but is preferably 250 μm or more and 600 μm or less, and more preferably 300 μm or more and 550 μm or less. The lower limit of the thickness (total thickness) of the sealing material sheet 1 according to this embodiment is preferably 250 μm or more, and more preferably 300 μm or more. The upper limit of the thickness (total thickness) of the sealing material sheet 1 according to this embodiment is preferably 600 μm or less, and more preferably 550 μm or less.

[0031] The thickness of the skin layer (first skin layer 12a) arranged on the functional layer lamination side in the sealing material sheet 1 according to this embodiment is not particularly limited, but is preferably 1 / 20 to 1 / 3 of the total thickness of the sealing material sheet 1, and more preferably 1 / 15 to 1 / 4. This more effectively suppresses the occurrence of irregularities on the surface of the skin layer (first skin layer 12a), and even when a functional layer is laminated on the surface of the skin layer (first skin layer 12a), the adhesion to the functional layer can be further improved.

[0032] The thickness of the core layer 11 in the sealing sheet 1 according to this embodiment is not particularly limited, but is preferably 200 μm or more and 400 μm or less, and more preferably 250 μm or more and 350 μm or less. The lower limit of the thickness of the core layer 11 in the sealing sheet 1 according to this embodiment is preferably 200 μm or more, and more preferably 250 μm or more. The upper limit of the thickness of the core layer 11 in the sealing sheet 1 according to this embodiment is preferably 400 μm or less, and more preferably 350 μm or less.

[0033] When a second skin layer 12b is laminated on the substrate side of the sealing material sheet 1 according to this embodiment, the thickness of the second skin layer 12b is not particularly limited, but it is preferably 1 / 20 to 1 / 3 of the total thickness of the sealing material sheet 1, and more preferably 1 / 15 to 1 / 4. This further enhances adhesion to other laminated components such as substrates and processors.

[0034] A sealing sheet can be made that has a skin layer containing a polypropylene resin (first skin layer 12a), and a functional layer is provided on the surface of this skin layer, thereby improving adhesion to the functional layer. The surface roughness Ra of the skin layer containing the polypropylene resin is preferably 15.0 μm or less, and more preferably 12.0 μm or less. If the surface roughness Ra of the skin layer is 10.0 μm or less, it is possible to further improve adhesion to the functional layer.

[0035] Furthermore, the encapsulating sheet for system boards on which processors are mounted may be applied to computer boards, desktop computers, notebook computers, and other computers used in data centers that handle large amounts of data on the cloud. It may also be applied to miniaturized electronic devices such as tablet computers, smartphones, telephones (including mobile phones and landline phones), game consoles (including portable and home game consoles), music players, car navigation systems, and PDAs. In addition, it may be applied to system boards on which processors for various home appliances and transportation control systems are mounted.

[0036] The following describes the sealing material composition used in the manufacture of the core layer 11 and skin layers (first skin layer 12a, second skin layer 12b) that constitute the sealing material sheet 1 according to this embodiment. The sealing material sheet 1 according to this embodiment can be manufactured, for example, by melt-molding the sealing material composition described in detail below, although this will be described in more detail later.

[0037] [Sealing material composition for core layer formation] The encapsulant composition for forming the core layer used in the manufacture of the "encapsulant sheet" according to this embodiment is a resin composition with a polyethylene-based resin (preferably a low-density polyethylene-based resin) as the base resin. In this specification, "base resin" refers to the resin with the highest content ratio among the resin components of a resin composition containing the base resin. When a mixture of the same type of resin with different densities (for example, multiple polyethylenes with different densities) is used as the base resin, the entire mixed resin is considered the base resin.

[0038] The base resin of the encapsulant composition for forming the core layer can be a wide variety of polyethylene-based resins. In particular, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or metallocene-based linear low-density polyethylene (M-LLDPE), as well as various other polyethylene-based resins, can be preferably used.

[0039] The density of the polyethylene resin used as the base resin of the "sealing material composition for core layer formation" is 0.880 g / cm 3 or more and 0.930 g / cm 3 or less, preferably 0.880 g / cm 3 or more and 0.925 g / cm 3 or less, preferably 0.880 g / cm 3 or more and 0.920 g / cm 3 or less is more preferable. The upper limit of the density of the above polyolefin resin used as the base resin of the "sealing material composition for core layer formation" is preferably 0.930 g / cm 3 or less, preferably 0.925 g / cm 3 or less, preferably 0.920 g / cm 3 or less is more preferable. By setting the density of the base resin of the sealing material composition to 0.880 g / cm 3 or more, the heat resistance of the sealing material sheet can be stably improved to a sufficient level. Also, by setting the same density to 0.930 g / cm 3 or less, the adhesiveness to other laminated members such as a substrate and a processor can be enhanced.

[0040] The MFR of the polyethylene resin used as the base resin of the "sealing material composition for core layer formation" is not particularly limited, but is preferably 2.0 g / 10 min or more and 5.0 g / 10 min or less, more preferably 2.2 g / 10 min or more and 4.5 g / 10 min or less, and even more preferably 2.3 g / 10 min or more and 4.0 g / 10 min or less. When the MFR of the polyethylene resin used as the base resin of the "sealing material composition for core layer formation" is 5.0 g / 10 min or less, the heat resistance required for the sealing material sheet can be provided, and when the MFR of the polyethylene resin used as the base resin of the "sealing material composition for core layer formation" is 2.0 g / 10 min or more, the molding characteristics required for the sealing material sheet can be provided.

[0041] Furthermore, the term "polyethylene resin" in this specification includes not only ordinary polyethylene obtained by polymerizing ethylene, but also resins obtained by polymerizing compounds having ethylenically unsaturated bonds such as α-olefins, resins obtained by copolymerizing multiple different compounds having ethylenically unsaturated bonds, and modified resins obtained by grafting other chemical species onto these resins.

[0042] In particular, a silane copolymer (silane-modified resin) obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as comonomers can be preferably used as part of the base resin of the core layer formation encapsulant composition. By using such a resin, sufficient adhesion can be obtained between the encapsulant sheet and other laminated components such as the substrate or processor, especially when the core layer is in contact with the substrate.

[0043] The content of the ethylenically unsaturated silane compound in a copolymer of α-olefin and an ethylenically unsaturated silane compound (silane-modified resin) is preferably, for example, 0.001% by mass or more and 15% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, and even more preferably 0.05% by mass or more and 2% by mass or less, relative to the total mass of the copolymer. The lower limit of the content of the ethylenically unsaturated silane compound in a copolymer of α-olefin and an ethylenically unsaturated silane compound (silane-modified resin) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.05% by mass or more, relative to the total mass of the copolymer. The upper limit of the content of the ethylenically unsaturated silane compound in a copolymer of α-olefin and an ethylenically unsaturated silane compound (silane-modified resin) is preferably 15% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, relative to the total mass of the copolymer.

[0044] [Other additives] Adhesion enhancers may be added to the sealing material composition as appropriate. Known silane coupling agents can be used as adhesion enhancers, but silane coupling agents having epoxy groups (hereinafter also referred to as "epoxy-based silane coupling agents") or silane coupling agents having mercapto groups (hereinafter also referred to as "mercapto-based silane coupling agents") can be used particularly preferably.

[0045] The sealing material composition may contain other components. Examples of such components include a weather-resistant masterbatch for providing weather resistance to the sealing material sheet, a thermally conductive filler, a crosslinking agent, a crosslinking aid, a light stabilizer, an ultraviolet absorber, a heat stabilizer, a flame retardant, a colorant, an antioxidant, a nucleating agent, and so on.

[0046] Among these, the inclusion of a thermally conductive filler allows for the dissipation of heat generated from various components such as processors. Examples of thermally conductive fillers include metal oxides such as zinc oxide, magnesium oxide, aluminum oxide, and titanium oxide, metal nitrides such as aluminum nitride and boron nitride, silicon compounds such as silicon oxides, and diamond.

[0047] When other components are included in the sealing material composition, their content will vary depending on their particle shape, density, etc., but it is preferable that each component be within a range of approximately 0.001% by mass or more and 5% by mass or less in the sealing material composition.

[0048] [Sealant composition for the first skin layer] The sealing material composition for the skin layer (first skin layer) arranged on the functional layer lamination side used in the manufacture of the "sealing material sheet" according to this embodiment is a resin composition that includes a polypropylene resin (preferably unstretched polypropylene) as the base resin.

[0049] The polypropylene resin is, for example, contained in an amount of 50% by mass or more of the total amount of the base resin. Preferably, homopolypropylene (homoPP) resin is used as the polypropylene resin. HomoPP is a polymer consisting solely of polypropylene and has high crystallinity, resulting in excellent rigidity. By using this for the first skin layer positioned on the functional layer lamination side, the occurrence of irregularities on the surface of the first skin layer can be effectively suppressed, thereby improving adhesion to the functional layer even when the functional layer is laminated on the surface of the first skin layer.

[0050] The density of the polypropylene resin used as the base resin for the "sealant composition for the first skin layer" is 0.890 g / cm³. 3 More than 0.930g / cm 3 Preferably, it is 0.890 g / cm³. 3 More than 0.925g / cm 3 Preferably, it is 0.890 g / cm³. 3 More than 0.920g / cm 3 The following is more preferable: The upper limit of the density of the polypropylene resin used as the base resin for the "sealant composition for the first skin layer" is 0.930 g / cm³. 3 Preferably, it is 0.925 g / cm³. 3 Preferably, it is 0.920 g / cm³. 3 The following is more preferable:

[0051] The MFR at 230°C of the polypropylene resin used as the base resin for the "sealing material composition for the first skin layer" is not particularly limited, but is preferably 2.0 g / 10 min or more and 20.0 g / 10 min or less, more preferably 4.0 g / 10 min or more and 17.0 g / 10 min or less, and even more preferably 5.0 g / 10 min or more and 15.0 g / 10 min or less. By having an MFR of 20.0 g / 10 min or less for the polypropylene resin used as the base resin for the "sealing material composition for the first skin layer," the occurrence of irregularities on the surface of the skin layer can be more effectively suppressed, so that even if a functional layer is laminated on the surface of the skin layer, the adhesion to the functional layer can be further improved. By having an MFR of 2.0 g / 10 min or more for the polypropylene resin used as the base resin for the "sealing material composition for the first skin layer," the formation of the skin layer becomes easier.

[0052] The polypropylene resin content is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total amount of the base resin.

[0053] Furthermore, the "sealant composition for the first skin layer" may contain a resin other than a polypropylene resin. As a resin other than a polypropylene resin, a wide range of polyethylene resins that can be used as a base resin for the sealant composition for forming the core layer can be selected.

[0054] The content of resins other than polypropylene resins is preferably less than 40% by mass of the total amount of base resin, more preferably less than 35% by mass, and even more preferably less than 30% by mass.

[0055] [Sealant composition for the second skin layer] The sealing material composition for the skin layer (second skin layer 12b) placed on the substrate lamination side used in the manufacture of the "sealing material sheet" according to this embodiment can be the same as the sealing material composition for core layer formation described above.

[0056] Similar to the encapsulant composition for forming the core layer described above, a "silane copolymer (silane-modified resin) obtained by copolymerizing α-olefin and an ethylenically unsaturated silane compound as comonomers" can preferably be used as part of the base resin of the encapsulant composition. By using such a resin, sufficient adhesion strength can be obtained between the "encapsulant sheet" and other laminated components such as substrates and processors.

[0057] Furthermore, by including a silane copolymer (silane-modified resin) as part of the base resin of the encapsulant composition, it is possible to provide sufficient adhesive strength between other laminated members and the "encapsulant sheet" while also providing peelability to the substrate. This makes it possible to reattach the encapsulant sheet to the system substrate during system substrate manufacturing, and to promote the reuse (recycling) of some components such as the encapsulant sheet and various components mounted on the system substrate, by peeling off the encapsulant sheet relatively easily without damaging the various components mounted on the system substrate.

[0058] The preferred content of the ethylenically unsaturated silane compound when constructing a copolymer (silane-modified resin) of α-olefin and an ethylenically unsaturated silane compound is the same as that of the sealing material composition for core layer formation described above.

[0059] The encapsulant composition for the skin layer (second skin layer) placed on the substrate stacking side may contain other additive components. The types and preferred amounts of other additive components are the same as those for the encapsulant composition for core layer formation described above.

[0060] <Method for manufacturing sealing material sheets> The "sealing material sheet" according to this embodiment can be manufactured by melt molding the "sealing material composition" described in detail above. The melt molding of the sealing material composition can be carried out by known molding methods, specifically, by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. As an example of a method for forming a sheet when the sealing material sheet is a multilayer sheet, a method of molding by co-extrusion using three types of melt-kneading extruders can be mentioned. The lower limit of the molding temperature during molding should be a temperature that exceeds the melting point of the sealing material composition.

[0061] In the manufacture of the sealing sheet, the melt molding temperature is preferably 30°C or higher than the melting point of the resin with the highest melting point among the base resins of the sealing composition contained in the sealing composition. Specifically, a high temperature of 175°C to 230°C is preferred, and a high temperature in the range of 190°C to 210°C is more preferred.

[0062] Even when the encapsulant composition contains a small amount of crosslinking agent (for example, less than 0.5% by mass), the gel fraction of the resulting encapsulant sheet is 25% or less, preferably 10% or less, and more preferably 1% or less, including zero. In particular, setting it to 10% or less effectively prevents gel generation during film formation and improves film formation performance. Furthermore, setting it to 1% or less improves the embedding ability of the encapsulant sheet in the modularization process, i.e., its ability to follow uneven surfaces.

[0063] ≪2. System Board≫ As shown in Figure 2, the system board 10 according to this embodiment has a processor 21 arranged and mounted on a substrate 20, and the system board 10 according to this embodiment includes a sealing material sheet 1 that covers the processor and is laminated on the substrate.

[0064] More specifically, if the sealing sheet consists of two layers, a core layer and a skin layer (first skin layer), the system substrate 10 is laminated on the substrate 20 and the processor 21 such that the core layer is positioned on the substrate lamination side and the skin layer (first skin layer) is positioned on the functional layer lamination side.

[0065] Furthermore, if the sealing sheet is composed of three layers having a first skin layer, a core layer, and a second skin layer, the sealing sheet 1 is laminated on the substrate 20 and the processor 21 such that the second skin layer is positioned on the substrate lamination side and the first skin layer is positioned on the functional layer lamination side.

[0066] The system substrate 10 can be manufactured by sequentially stacking components including a sealing material sheet, integrating them by vacuum suction or the like, and then heat-pressing the components together as a single molded body using a molding method such as lamination.

[0067] Furthermore, a functional layer 30 can be arranged and laminated on the surface of the first skin layer 12a of the system substrate according to this embodiment. The functional layer 30 is not particularly limited, but examples include an electromagnetic reflection shield capable of reflecting electromagnetic waves and suppressing electromagnetic interference, and a heat dissipation pad or heat sink for dissipating heat generated from various components such as a processor.

[0068] Another method for providing a functional layer on the surface of a skin layer containing a polypropylene resin as the base resin is to laminate it via an adhesive. By laminating the skin layer and the functional layer via an adhesive layer, release properties can be provided to the functional layer. This makes it possible to peel off the functional layer relatively easily without damaging the functional layer or the encapsulating sheet, thereby promoting the reattachment of the functional layer to the encapsulating sheet during system substrate manufacturing or the reuse (recycling) of the functional layer. [Examples]

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0070] <Manufacturing of sealing sheets for system boards> As base resins, polyethylene resins 1-5 (referred to as "PE1-5" in the table) and polypropylene resin (referred to as "PP" in the table) were prepared. The densities, number of moles of α-olefin, number of carbon atoms, and MFR at 190°C for PE1-5 and PP are shown in Table 1.

[0071] [Table 1]

[0072] Of the polyethylene resins 1 to 5 mentioned above, PE1 was a silane-modified polyethylene resin obtained as follows. Specifically, this silane-modified polyethylene resin PE1 has a density of 0.898 g / cm³. 3 It was obtained by mixing 95 parts by mass of a metallocene-based linear low-density polyethylene resin with an MFR of 3.5 g / 10 min with 5 parts by mass of vinyltrimethoxysilane and 0.15 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200°C.

[0073] Furthermore, in the table above, PE5 is low-density polyethylene resin (LDPE), and PP is homopolymer resin.

[0074] The encapsulant composition raw materials described below were mixed in the proportions shown in Table 2 to obtain the encapsulant compositions for the Examples and Comparative Examples, respectively. Each encapsulant composition was extruded using a φ30 mm extruder and a film molding machine with a 200 mm wide T-die at an extrusion temperature of 210 °C and a take-up speed of 1.1 m / min to produce resin sheets. These resin sheets were then used to manufacture the encapsulant sheets for the Examples and Comparative Examples. The thickness of each encapsulant sheet in the Examples and Comparative Examples was 450 μm in total. In Table 2, the content of PE1-5 and PP is the content (parts by mass) per 100 parts by mass of the base resin, while the content of other additives (silane coupling agent, crosslinking agent, UV absorber, light stabilizer) is the content (mass %) in the total amount of the encapsulant composition.

[0075] In Examples 1 and 2, the sealing sheet was configured with two layers (first skin layer / core layer), in Example 3, the sealing sheet was configured with three layers (first skin layer / core layer / second skin layer), and in Comparative Examples 1 and 2, the sealing sheet was configured with a single layer.

[0076] [Table 2]

[0077] The UV absorber listed in Table 2 is KEMISORB79. The light stabilizer listed in Table 2 is KEMISTAB62(HALS).

[0078] For the sealing material sheets of the examples and comparative examples listed in Table 2, the Vicat softening point, Shore A hardness (JIS K6253), melt viscosity, thickness, volume resistivity, water absorption rate, water vapor permeability, and gel fraction were measured. These measurement results are shown in Table 3.

[0079] The Vicat softening point was measured using the 533HDT test apparatus 6M-2 manufactured by Toyo Seiki Seisakusho. Shore A hardness was measured using the ESCO EA617DK-1. The melt viscosity was measured using a Capillograph 1D PMD-C manufactured by Toyo Seiki Seisakusho. For volume resistivity, an ADC 5450 digital ultra-high resistance / micro-current meter was used, and the value was measured after 30 seconds at an applied voltage of 500V in an environment of 23°C, in accordance with JIS K6911-1995. Regarding the water absorption rate, the sealing material sheet, which was used as the test specimen, was immersed in 60°C water (deionized water), and the water absorption rate ((Aba-Abb) / Abb×100)(%) was calculated from the ratio of the increase in weight Aba when saturated to the weight Abb before immersion in water (deionized water) (in the dry state). Water vapor transmission rate 1 (g / m³) 2The water vapor transmission rate was measured using a water vapor transmission rate measuring device (manufactured by Mokon, product name "PERMATORAN-W 3 / 31") at 40°C and 90% RH, in accordance with JIS K 7129 Method B. Water vapor transmission rate 2 (g / m³) 2 The water vapor transmission rate was measured using a water vapor transmission rate measuring device (manufactured by Mokon, product name "PERMATORAN-W 3 / 31") at 50°C and 90%RH, in accordance with JIS K 7129 Method B. The gel fraction was determined by placing 0.1g of the sealing material sheet into a resin mesh, extracting it in toluene at 60°C for 4 hours, then removing the resin mesh, drying it, weighing it, and comparing the mass before and after extraction to measure the mass percentage of residual insoluble matter.

[0080] <Evaluation Example 1: Molding Characteristics 1> A lead wire (250 μm diameter) was placed on the surface of a flat white tempered glass board. The lead wire was then covered with laminated 150 mm x 150 mm encapsulating material sheets from both the example and comparative example. These laminated sheets were then subjected to vacuum heating and lamination (vacuum lamination) at a set temperature of 150°C, with a vacuum applied for 3 minutes, followed by the release of atmospheric pressure from the upper chamber and vacuum pressurization for 7 minutes. Evaluation samples were obtained for each example and comparative example. The resin temperature (reached temperature) of the encapsulating material sheet during lamination was 147°C. These evaluation samples were visually observed, and the molding characteristics were evaluated according to the following evaluation criteria. (Evaluation Criteria) A: The sealing sheet perfectly conformed to the irregularities of the opposing substrate surface. No void formation was observed. B: 2mm 2 Five or fewer bubbles were observed within the specified range. C: A portion of the sealing material sheet did not fully conform to the unevenness of the opposing substrate surface, resulting in some lamination defects (gaps) near the lead wires. The evaluation results are recorded in the table below as "Molding Characteristics 1".

[0081] <Evaluation Example 2: Molding Characteristics 2> Except for simulating a CPU, the molding characteristics were evaluated using the same method and evaluation criteria as in Molding Characteristics 1 described above, with the exception that epoxy-like chip-shaped molded bodies, 2 cm long, 1.5 cm wide, and 1.5 mm thick, were arranged in a 3x3 configuration on a 1.2 mm thick glass epoxy substrate with a 3 mm gap between them. The evaluation results are listed in the table below as "Molding Characteristics 2".

[0082] <Evaluation Example 3: Moisture and Heat Resistance Adhesion Maintenance Rate> On a 1.2 mm thick glass epoxy substrate, 450 μm thick sealing material sheets of the examples and comparative examples were vacuum laminated using a diaphragm-type vacuum laminator with upper and lower chambers under the following conditions: temperature 150°C, vacuuming for 5 minutes (vacuuming from 100 kPa to 0.1 Pa or less in both upper and lower chambers), pressing time 10 seconds (upper chamber pressure: pressing from 0.1 Pa to 100 kPa over 10 seconds, maintaining a pressure of 0.1 Pa or less in the lower chamber), and holding press for 7 minutes (upper chamber pressure: 100 kPa, lower chamber pressure: maintaining a pressure of 0.1 Pa or less). After cooling to room temperature, the sheets were stored in a humid heat test environment of 85°C and 85% humidity. The sealing material sheets of the examples and comparative examples were then cut to a width of 15 mm, and the adhesion strength was measured by peeling at 180 degrees using a Tensilon universal material tester (manufactured by A&D Co., Ltd.). Then, the retention rate (Adb / Adb × 100) (%) is calculated from the ratio of the adhesion strength Ada after the moist heat test to the adhesion strength Adb before the moist heat test, and is recorded as "Moisture Heat Resistance Retention Rate" in the table below.

[0083] <Evaluation Example 4: Heat-resistant creep> To evaluate heat resistance, a "heat creep test" was conducted using the method described below. In the "heat creep test," one sheet of sealing material cut to a size of 75 mm x 50 mm and one sheet of semi-tempered glass measuring 75 mm x 50 mm were layered on a 250 mm square sheet of semi-tempered glass. The layers were then pressed together at 150°C for 15 minutes using a vacuum laminator used for manufacturing solar cell modules. The laminated sample was then placed upright in a 140°C oven for 12 hours, and the displacement distance (mm) of the semi-tempered glass was measured. The measurement results are shown in the table below as "heat creep resistance."

[0084] <Evaluation Example 5: Evaluation of Adhesion to Functional Layers> The adhesion of the encapsulating sheets of Examples 1-3 and Comparative Examples 1 and 2 to the functional layer (electromagnetic wave shielding layer: a grid-like electromagnetic wave shielding material formed by laminating copper foil (12 μm thick) and PET (100 μm thick) with a two-component curing adhesive, and then forming it by photolithography, with a copper foil line width of 100 μm and a width of 2 mm without copper foil) was evaluated. Specifically, the encapsulating sheets of Examples 1-3 were integrally molded by laminating them onto the substrate so as to cover the processor, with the surface of the encapsulating sheet without the first skin layer (the substrate lamination side) facing the surface of the system substrate on which the processor is mounted. Then, an electromagnetic wave reflective sheet was attached as a functional layer to the surface of the first skin layer located on the uppermost surface of the system substrate via a 25 μm thick adhesive layer formed with an acrylic adhesive, and the adhesion between the encapsulating sheet and the functional layer was evaluated according to the evaluation criteria below. The evaluation results are shown in the table below as "Adhesion".

[0085] For Comparative Examples 1 and 2, which lack the first skin layer, the encapsulating sheets were integrally molded by laminating them onto the substrate so as to cover the processor, with one surface of the encapsulating sheet facing the surface of the system substrate on which the processor is mounted. An electromagnetic wave reflective sheet was then attached to the uppermost surface of the encapsulating sheet on the system substrate as a functional layer, and the adhesion between the encapsulating sheet and the functional layer was evaluated according to the evaluation criteria below.

[0086] [Evaluation Criteria] ○: The sealing sheet and the functional layer were in close contact without any gaps. ×: A partial gap was present between the sealing sheet and the functional layer.

[0087] <Evaluation Example 6: Release Properties Evaluation> The sealing material sheets of the examples and comparative examples that were adhered in Evaluation Example 5 were left for 168 hours in an environment of 23°C and 60% Rh. After that, the functional layer was peeled off, and the release properties of the functional layer were visually evaluated. The evaluation results are shown in the table below as "Release Properties".

[0088] [Evaluation Criteria] ○: The functional layer was cleanly released at the interface between the sealing sheet and the functional layer. ×: At the interface between the sealing sheet and the functional layer, the functional layer did not release cleanly, and the release surface tore.

[0089] [Table 3]

[0090] As can be seen from the table above, the encapsulating material sheet has a multilayer structure comprising a core layer containing polyethylene resin as the base resin and a skin layer containing polypropylene resin as the base resin. This structure suppresses the formation of partial gaps between the encapsulating material sheet and the functional layer when a functional layer is laminated on the surface of the encapsulating material sheet, thereby improving adhesion to the functional layer. [Explanation of Symbols]

[0091] 1. Sealing sheet 11 Core Layers 12 skin layers 12a First skin layer 12b Second skin layer 10 System Boards 20 circuit boards 21 processors

Claims

1. A sealing sheet for a system board on which a processor is mounted, It has a multilayer structure consisting of a core layer and a skin layer. The core layer contains polyethylene resin as the base resin, The Vicat softening point is in the range of 30°C to 100°C. Sealing sheet.

2. The surface roughness Ra of the skin layer is 15 μm or less. The sealing sheet according to claim 1.

3. A system board equipped with a processor, circuit board and A processor disposed on the surface of the substrate, A sealing sheet according to claim 1 or 2, Equipped with, The sealing sheet is laminated on the substrate, covering the processor, such that the core layer is located closer to the substrate than the skin layer. System board.

4. The sealing sheet is provided with a functional layer on the surface of the skin layer. The system board according to claim 3.

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