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

Abstract

The present invention provides a sealing sheet that offers a desirable level of molding properties for use as a sealing sheet for system boards on which processors are mounted, and that can enhance adhesion to other laminated components such as substrates and processors. [Solution] A sealing sheet for a system board on which a processor is mounted, wherein the base resin is a polyolefin resin, the melting point is 90°C or higher and 120°C or lower, and the temperature difference between the extracellular melting start temperature and the melting point is 20°C or lower.

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

[0004] For example, Patent Document 1 describes a technology relating to an epoxy resin composition for a semiconductor device, comprising a semiconductor element 1, a substrate on which the semiconductor element is mounted, and an epoxy resin composition, wherein the epoxy resin composition is molded to one side of the substrate.

[0005] Patent Document 1 describes that this epoxy resin composition is excellent in adhesion and reliability while enabling miniaturization and performance improvement of resin-encapsulated semiconductor devices. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-212338 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a sealing sheet that has a desirable level of molding properties for use as a sealing sheet for a system substrate on which a processor is mounted, and that can enhance adhesion to other laminated components such as substrates and processors. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have discovered that the above problem can be solved by specifying the base resin constituting the encapsulating material sheet for the system substrate on which the processor is mounted as a resin in which the temperature difference between the extracellular melting initiation temperature and the melting point is below a predetermined value, and have completed the present invention. Specifically, the present invention provides the following.

[0009] (1) A sealing sheet for a system board on which a processor is mounted, wherein the base resin is a polyolefin resin, the melting point is 90°C or higher and 120°C or lower, and the temperature difference between the extracellular melting initiation temperature and the melting point is 20°C or lower.

[0010] (2) The gel fraction is 10% or less. (1) The sealing sheet described above.

[0011] (3) Contains silane-modified polyethylene resin The sealing sheet described in (1) or (2).

[0012] (4) A multilayer structure comprising a core layer and a skin layer, The skin layer contains a silane-modified polyethylene resin. The sealing sheet described in (1) or (2).

[0013] (5) A system board equipped with a processor, circuit board and A processor disposed on the surface of the substrate, (1) or (2) the sealing material sheet, Equipped with, The sealing sheet is laminated on the substrate, covering the processor. System substrate.

Advantages of the Invention

[0014] The encapsulant sheet of the present invention has a preferable level of moldability as an encapsulant sheet for a system substrate on which a processor is mounted, and has high adhesiveness to other laminated members such as a substrate and a processor.

Brief Description of the Drawings

[0015] [Figure 1] It is a cross-sectional view schematically showing the layer structure of the encapsulant sheet of one embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of the layer structure of the encapsulant sheet of one embodiment of the present invention and a system substrate on which a processor is mounted. [Figure 3] It is a graph showing the melting point and the extrapolated melting start temperature of the "encapsulant sheet for system substrate (Example 3)" of one embodiment of the present invention.

Modes for Carrying Out the Invention

[0016] Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0017] ≪1. Encapsulant sheet≫ The encapsulant sheet according to the present embodiment is an encapsulant sheet for a system substrate on which a processor is mounted. Specifically, in a system substrate, in order to protect various components arranged and mounted on the substrate such as a processor from physical impact, it is a resin sheet that can be used as an encapsulant sheet for covering and laminating various components such as a processor.

[0018] And the encapsulant sheet according to the present embodiment is characterized in that it uses a polyolefin resin as a base resin, has a melting point of 90°C or higher and 120°C or lower, and the temperature difference between the extrapolated melting start temperature and the melting point is 20°C or lower.

[0019] In this specification, the terms "polyolefin resin," etc., are used to include not only "polyolefin resin" but also copolymers that contain, for example, 50% or more (preferably 70% or more, more preferably 80% or more) of the polyolefin main chain, and in which a portion of the main chain is replaced by another main chain different from that of polyolefin.

[0020] By incorporating such polyolefin resins as a base resin, it is possible to enhance adhesion to other laminated components such as substrates and processors while providing a desirable level of molding properties for a system substrate encapsulant sheet. Regarding the thermal properties of the encapsulant sheet, not only is the melting point range optimized, but by also specifying the temperature difference of the encapsulant sheet within the aforementioned range, desirable characteristics such as molding properties required for a system substrate encapsulant sheet can be provided. Furthermore, heat resistance can be provided at the finished product stage, when the system substrate is mounted with the processor attached.

[0021] For example, our research has revealed that even in the case of a sealing material sheet with a polyolefin resin as the base resin, and even if the melting point is 90°C or higher, if the temperature difference between the extracellular melting initiation temperature and the melting point becomes larger than a certain value, it will have an adverse effect on the molding properties.

[0022] Herein, the melting point of the sealing material sheet as used herein refers to the melting peak temperature measured by differential scanning calorimetry (DSC) at the stage after the completion of sheet formation of a sealing material sheet, which is formed by a molding method such as extrusion melt molding, from a sealing material composition comprising a resin component and other additives.

[0023] Furthermore, the extracellular melting initiation temperature of the encapsulant sheet refers to the value obtained in accordance with the method described in JIS K 7121-1987 "Method for Measuring Transition Temperatures of Plastics". Specifically, for the encapsulant sheet in the uncrosslinked stage after film formation, the melting peak temperature is determined by DSC, and the extracellular melting initiation temperature is defined as the temperature at the intersection of a straight line extending from the low-temperature baseline to the high-temperature side and a tangent line drawn at the point where the slope is maximum on the low-temperature side curve of the melting peak (if two or more overlapping melting peaks appear, the melting peak with the lower melting peak temperature is used).

[0024] The temperature difference between the extracellular melting initiation temperature and the melting point in the sealing material sheet according to this embodiment may be 20°C or less, but is preferably 17°C or less, and more preferably 15°C or less.

[0025] Furthermore, having a melting point of 90°C or higher for the sealing material sheet improves its heat resistance against heat generated from various components such as processors. Having a melting point of 120°C or lower for the sealing material sheet makes it easier to form the sealing material sheet into a sheet.

[0026] The melting point of the sealing material sheet according to this embodiment may be 90°C or higher and 120°C or lower, but is preferably 95°C or higher and 117°C or lower, and more preferably 100°C or higher and 115°C or lower. The lower limit of the melting point of the sealing material sheet according to this embodiment is preferably 95°C or higher, and more preferably 100°C or higher. The upper limit of the melting point of the sealing material sheet according to this embodiment is preferably 117°C or lower, and more preferably 115°C or lower.

[0027] The MFR of the sealing sheet according to this embodiment is not particularly limited, but is preferably 2.0 g / 10 min or more and 5.0 g / 10 min or less on average across all layers, 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. The lower limit of the MFR of the sealing sheet according to this embodiment is preferably 2.0 g / 10 min or more on average across all layers, more preferably 2.2 g / 10 min or more, and even more preferably 2.3 g / 10 min or more. The upper limit of the MFR of the sealing sheet according to this embodiment is preferably 5.0 g / 10 min or less on average across all layers, more preferably 4.5 g / 10 min or less, and even more preferably 4.0 g / 10 min or less. A sealing sheet with an MFR of 5.0 g / 10 min or less can provide the sealing sheet with the necessary heat resistance, and a sealing sheet with an MFR of 2.0 g / 10 min or more can provide the sealing sheet with the necessary molding characteristics.

[0028] In this specification, "MFR" of a sealing material sheet refers to the MFR of a sealing material sheet formed by a molding method such as extrusion melt molding from a sealing material composition containing resin components and other additives, after the completion of sheet formation, i.e., in the uncrosslinked state after film formation, measured under conditions of 190°C and a 2.16 kg load in accordance with JIS K7210. In the case of a sealing material sheet being a multilayer film, the MFR of the multilayer sealing material sheet shall be the value obtained by performing the above-mentioned measurement while all layers are integrally laminated in a multilayer state.

[0029] The Vicat softening point of the sealing material sheet is not particularly limited, but is preferably 30°C to 100°C, more preferably 35°C to 95°C, and even more preferably 40°C to 90°C. The lower limit of the Vicat softening point of the sealing material sheet 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 material sheet is preferably 100°C or lower, more preferably 95°C or lower, and even more preferably 90°C or lower.

[0030] The sealing sheet 1 according to this embodiment may be a single layer, but it may also be a multilayer film with a multilayer structure comprising a core layer 11 and two skin layers 12 on both sides of the core layer 11. When the "sealing sheet" is a multilayer film, it is more preferable to have a layer configuration in which the MFR differs for each layer, within the range that satisfies the essential constituent requirements of the present invention. Specifically, as shown in Figure 1, it is preferable to place the layer with the lower MFR in the center as the core layer 11, and the layer with the higher MFR on the outermost layer side as the skin layer 12. Even when the sealing sheet according to this embodiment is a single layer sealing sheet, it has sufficiently good molding properties, but by placing the layer with the relatively higher MFR as the skin layer 12 in this way, the sealing sheet can further improve its molding properties while increasing its adhesion to other laminated members such as substrates and processors.

[0031] The thickness (total thickness) of the sealing material sheet according to this embodiment is not particularly limited, 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 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 according to this embodiment is preferably 600 μm or less, and more preferably 550 μm or less. If the thickness is 250 μm or more, for example, even if the sealing material sheet 1 is thinned to a total thickness of about 250 μm, it is possible to achieve a sufficiently desirable combination of molding characteristics and heat resistance. If the total thickness exceeds 600 μm, no further improvement in the impact mitigation effect can be obtained, so it is preferable that the total thickness be 600 μm or less.

[0032] Furthermore, when the sealing material sheet according to this embodiment is a multilayer film sealing material sheet 1, the thickness of the core layer 11 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. When the sealing material sheet according to this embodiment is a multilayer film sealing material sheet 1, the lower limit of the thickness of the core layer 11 is preferably 200 μm or more, and more preferably 250 μm or more. When the sealing material sheet according to this embodiment is a multilayer film sealing material sheet 1, the upper limit of the thickness of the core layer 11 is preferably 400 μm or less, and more preferably 350 μm or less.

[0033] When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the thickness of each layer of the skin layer 12 is not particularly limited, but is preferably 20 μm or more and 100 μm or less, and more preferably 25 μm or more and 80 μm or less. When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the lower limit of the thickness of each layer of the skin layer 12 is preferably 20 μm or more, and more preferably 25 μm or more. When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the upper limit of the thickness of each layer of the skin layer 12 is preferably 100 μm or less, and more preferably 80 μm or less.

[0034] When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the total thickness of the two skin layers 12 laminated on both sides of the core layer 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. When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the total thickness of the two skin layers 12 laminated on both sides of the core layer is preferably 1 / 20 or more of the total thickness of the sealing material sheet 1, and more preferably 1 / 15 or more. When the sealing material sheet according to this embodiment is a multilayer sealing material sheet 1, the total thickness of the two skin layers 12 laminated on both sides of the core layer is preferably 1 / 3 or less of the total thickness of the sealing material sheet 1, and more preferably 1 / 4 or less. By setting the thickness of each layer of the sealing material sheet 1 within this range, the heat resistance and molding characteristics of the sealing material sheet 1 can be maintained within a good range.

[0035] The surface of the encapsulating sheet provided on the system board (the surface of the encapsulating sheet on the opposite side of the board) may be flat without any irregularities, but it is preferable that the surface of the encapsulating sheet has irregularities such that the surface roughness Ra of the encapsulating sheet is 0.9 μm or more. This increases the surface area of ​​the encapsulating sheet, making it possible to effectively dissipate heat from various components such as the processor through the encapsulating sheet.

[0036] Furthermore, the surface roughness Ra of the sealing material sheet is preferably 1.2 μm or more, and more preferably 2.5 μm or more.

[0037] To ensure that the surface roughness Ra of the encapsulating material sheet provided on the system substrate is 0.9 μm or greater, one possible method is to process the sheet by extrusion molding, in which the resin extruded during film formation is sandwiched between an embossing roll and a rubber roll (or a metal roll) to create surface irregularities on the surface of a flat encapsulating material sheet.

[0038] 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.

[0039] The following describes the sealing material composition used in the manufacture of the sealing material sheet according to this embodiment. The sealing material sheet 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.

[0040] Sealing material composition The sealing material composition (hereinafter, also simply referred to as "sealing material composition") used for manufacturing the "sealing material sheet" according to this embodiment is a resin composition based on a polyolefin resin (preferably a low-density polyethylene resin). In this specification, the "base resin" refers to the resin having the largest content ratio among the resin components of the resin composition containing the base resin. When using a mixed resin of the same kind of resins with different densities (for example, a plurality of polyethylenes with different densities respectively), the entire mixed resin is regarded as the base resin.

[0041] Regarding the base resin of the sealing material composition, various polyolefin resins can be widely selected as long as the melting point is 90°C or higher and 120°C or lower, and the temperature difference between the supplementary melting start temperature and the melting point is within the range of 20°C or lower. Among them, in addition to low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or metallocene-based linear low-density polyethylene (M-LLDPE), various polyethylene resins can be preferably used.

[0042] The density of the above polyolefin resin used as the base resin of the "sealing material composition" is 0.880 g / cm 3 , 3 , 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, more preferably 0.880 g / cm 3 or more and 0.920 g / cm 3 or less. The upper limit of the density of the above polyolefin resin used as the base resin of the "sealing material composition" is preferably 0.930 g / cm 3 or less, preferably 0.925 g / cm 3 or less, more preferably 0.920 g / cm 3 or less. The density of the base resin of the sealing material composition is 0.880 g / cm 3By doing so, the heat resistance of the sealing sheet can be stably improved to a sufficient level. Furthermore, the density can be increased to 0.930 g / cm³. 3 By doing the following, "adhesion to other laminated components such as substrates and processors can be maintained at a sufficiently favorable level."

[0043] 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.

[0044] In particular, a silane copolymer (silane-modified resin) obtained by copolymerizing α-olefin and an ethylenically unsaturated silane compound as comonomers can be preferably 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.

[0045] 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 the laminated member 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 allowing the encapsulant sheet to be peeled off relatively easily without damaging the various components mounted on the system substrate.

[0046] 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 copolymer mass. 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 copolymer mass. 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 copolymer mass.

[0047] [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.

[0048] 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.

[0049] Among these, the inclusion of a thermally conductive filler allows for the dissipation of heat generated from the processor and other components. Examples of thermally conductive fillers include metal oxides such as zinc oxide, magnesium oxide, aluminum oxide, silicon oxide, and titanium oxide, as well as metal nitrides such as aluminum nitride, boron nitride, and silicon nitride, and diamond.

[0050] 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.

[0051] <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.

[0052] 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.

[0053] 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.

[0054] ≪2. System Board≫ As shown in Figure 2, the system board 10 according to this embodiment has a processor 21 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.

[0055] 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. [Examples]

[0056] 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.

[0057] <Manufacturing of sealing sheets for system boards> As base resins, polyethylene resins 1 to 6 (referred to as "PE1 to PE7" respectively in the table) were prepared. The densities, number of moles of α-olefin, number of carbon atoms, and MFR at 190°C for PE1 to PE7 are shown in Table 1.

[0058] [Table 1]

[0059] Of the polyethylene resins 1 to 7 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.

[0060] Furthermore, in the table above, PE5 refers to low-density polyethylene resin (LDPE), and EVA refers to ethylene-vinyl acetate copolymer resin.

[0061] The encapsulant composition raw materials described below were mixed in the proportions shown in Tables 2 and 3 to obtain the encapsulant compositions for the Examples and Comparative Examples, respectively. Each encapsulant composition was used to produce resin sheets 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. These resin sheets were then used to produce the encapsulant sheets for the Examples and Comparative Examples. The thickness of each encapsulant sheet for the Examples and Comparative Examples was 450 μm in total. In Tables 2 and 3, the content of PE1-7 and EVA 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.

[0062] In Examples 1 and 2, and Comparative Examples 1 to 3, the sealing sheet was a single-layer structure, while in Examples 3 to 8, the sealing sheet was a multi-layer structure (skin layer / core layer / skin layer).

[0063] [Table 2]

[0064] [Table 3]

[0065] The silane coupling agent in Tables 2 and 3 is vinyltrimethoxysilane. The crosslinking agent in Tables 2 and 3 is an organic peroxide (Luperox 101). The UV absorber listed in Tables 2 and 3 is KEMISORB79. The light stabilizer listed in Tables 2 and 3 is KEMISTAB62(HALS).

[0066] For the sealing material sheets of the examples and comparative examples described in Tables 2 and 3, the Vicat softening point, Shore A hardness (JIS K6253), melt viscosity, thickness, volume resistivity, water absorption rate, water vapor permeability, gel fraction, extrapolation melting onset temperature (JIS K 7121-1987), and melting point were measured. These measurement results are shown in Table 4.

[0067] 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) 2 The water vapor transmission rate was measured using a water vapor transmission rate measuring device (MOCON Corporation, 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) 2The water vapor transmission rate was measured using a water vapor transmission rate measuring device (manufactured by Mokon, product name "PERMATORAN-W 3 / 31") under measurement conditions of 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.

[0068] The melting point and extrapolation onset temperature of the sealing material sheet were measured using differential scanning calorimetry (DSC) based on JIS K 7121-1987. DSC measurements were taken within a temperature range of -80 to +200°C. Figure 3 shows the melting point and extrapolation onset temperature for the sealing material sheet of Example 3. In Figure 3, the vertical axis represents heat flow (heat capacity), and the horizontal axis represents temperature. From Figure 3, the melting point of the sealing material sheet of Example 3 is 107.6°C, and the extrapolation onset temperature is 94.8°C. Therefore, the temperature difference between the extrapolation onset temperature and the melting point is 12.8°C.

[0069] <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 listed in the table below as "Molding Characteristics 1".

[0070] <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".

[0071] <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 (Ada / 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.

[0072] <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."

[0073] [Table 4]

[0074] [Table 5]

[0075] As can be seen from the table above, the encapsulating sheet, which uses a polyolefin resin as the base resin, has a melting point of 90°C to 120°C, and a temperature difference of 20°C or less between the extracellular melting initiation temperature and the melting point, possesses a desirable level of molding properties as an encapsulating sheet for system substrates and exhibits high adhesion to other laminated components such as substrates and processors. In the case of Comparative Example 3, during the water absorption test at 60°C, the additive contained in the encapsulating material dissolved, resulting in a decrease in the weight Aba of the encapsulating material sheet after immersion in water (ion-exchanged water) compared to the weight Abb of the encapsulating material sheet before immersion (dry state). When calculated as the water absorption rate ((Aba-Abb) / Abb×100), it yielded a negative value. [Explanation of Symbols]

[0076] 1. Sealing sheet 11 Core Layers 12 skin layers 10 System Boards 20 circuit boards 21 processors

Claims

1. A sealing sheet for a system board on which a processor is mounted, Using polyolefin resin as the base resin, The melting point is between 90°C and 120°C, and the temperature difference between the extracellular melting initiation temperature and the melting point is 20°C or less. Sealing sheet.

2. The gel fraction is 10% or less. The sealing sheet according to claim 1.

3. Contains silane-modified polyethylene resin. The sealing sheet according to claim 1 or 2.

4. It has a multilayer structure consisting of a core layer and a skin layer. The skin layer contains a silane-modified polyethylene resin. The sealing sheet according to claim 1 or 2.

5. 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. System board.

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