Resin sheet

Abstract

To provide a novel resin sheet which can constitute a new heat dissipation structure having high dissipation effect.SOLUTION: There is provided a resin sheet, wherein the resin sheet contains a thermoplastic resin, a plate-like filler and a connection filler, and an average particle diameter of the connection filler is 2 μm or less. The resin sheet is the one resin sheet or a laminate of the two or more resin sheets, when pressure of 12 kPa is applied to a test piece 10 having a thickness of T0 in an environment at 100°C for 10 minutes in a thickness direction of the test piece 10, and a thickness T1 of the test piece 10 in a part where the pressure is applied is measured, an embedding percentage calculated by the following expression: R=(T0-T1) / T0×100 may be 30% or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A central processing unit (abbreviated as "CPU" in this specification) is one of the representative devices that make up a computer. The amount of heat generated by a CPU increases dramatically when the computer is in operation. In recent years, however, as electronic devices have become more powerful, smaller, and lighter, semiconductor packages have become more densely packed, LSIs have become more highly integrated, and processing speeds have increased, making it extremely important to take measures against the heat generated by electronic devices.

[0003] In a typical electronic device, a heat spreader is attached to a CPU placed on a circuit board via a thermal interface material (abbreviated as "TIM" in this specification), and the heat spreader is placed in contact with a heat sink. In this way, in the electronic device, heat generated by the CPU is conducted to the heat spreader via the TIM, and the heat is further conducted in the planar direction by the plate-like heat spreader, and the heat is dissipated to the outside of the electronic device via the heat sink (see Patent Document 1).

[0004] The reason why such a heat dissipation structure has been conventionally adopted for a CPU is as follows. A heat spreader is made of metal or graphite, and has high thermal conductivity in the surface direction and high heat dissipation, but does not conform to the object to be cooled (CPU), has insufficient adhesion to the object to be cooled (CPU), and is not insulating. On the other hand, a TIM has a certain degree of conformability to the object to be cooled (CPU), good adhesion, and is insulating, but has insufficient thermal conductivity. Therefore, by using a combination of these (heat spreader and TIM) and adopting the above-mentioned heat dissipation structure, these shortcomings are compensated for. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 139364 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in such conventional electronic devices, as long as the TIM is an essential component, the heat dissipation structure is limited, and the configuration of the electronic device is also limited. As an alternative to the TIM, it is appropriate to use a resin sheet, considering the need for insulation and conformability, but no resin sheet with a high heat dissipation effect has been known so far. Although the above explanation has been given using a CPU as an example, the same problem can occur in other devices that have a heat generating element similar to that of a CPU.

[0007] An object of the present invention is to provide a novel resin sheet capable of forming a new heat dissipation structure having a high heat dissipation effect. [Means for solving the problem]

[0008] The present invention employs the following configuration. [1] A resin sheet comprising a thermoplastic resin, a plate-like filler, and a connecting filler, the connecting filler having an average particle size of 2 μm or less. [2] A resin sheet, comprising a thermoplastic resin, a plate-like filler, and a connecting filler, the connecting filler having an average particle size of 2 μm or less, the resin sheet being one sheet or a laminate of two or more sheets of the resin sheet, and having a thickness of T 0 A test piece was used, and a pressure of 12 kPa was applied to the test piece in the thickness direction for 10 minutes in an environment of 100° C., and the thickness T 1 When the measurement was performed, the following formula: R=(T 0 -T 1 ) / T 0 ×100 The resin sheet has an embedment rate R of 30% or more.

[0009] [3] The resin sheet according to [1], wherein the resin sheet has a relative dielectric constant of 4 or less at a frequency of 10 GHz, as measured in accordance with a TM0m0 mode cavity resonator perturbation method. [4] The resin sheet according to [1] or [3], wherein the resin sheet has a dielectric tangent of 0.01 or less at a frequency of 10 GHz, as measured in accordance with a TM0m0 mode cavity resonator perturbation method.

[0010] [5] The resin sheet according to [1], [3] or [4], wherein the plate-like filler is made of boron nitride or aluminum oxide. [6] The resin sheet according to any one of [1] and [3] to [5], wherein the connecting filler is made of magnesium hydroxide. [7] The resin sheet according to any one of [1] and [3] to [6], wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer. [8] The resin sheet according to any one of [1] and [3] to [7], wherein the ratio of the content of the connected filler to the content of the flake filler in the resin sheet is 60 to 140 volume %. [9] The resin sheet according to any one of [1] and [3] to [8], wherein the flake filler has an average particle size of 5 μm or more.

[0011]

[10] The resin sheet according to [2], wherein the resin sheet has a relative dielectric constant of 4 or less at a frequency of 10 GHz, measured in accordance with a TM0m0 mode cavity resonator perturbation method.

[11] The resin sheet according to [2] or

[10] , wherein the resin sheet has a dielectric tangent of 0.01 or less at a frequency of 10 GHz, as measured in accordance with a TM0m0 mode cavity resonator perturbation method.

[12] The resin sheet according to [2],

[10] or

[11] , wherein the plate-like filler is made of boron nitride or aluminum oxide.

[13] The resin sheet according to any one of [2] and

[10] to

[12] , wherein the connecting filler is made of magnesium hydroxide.

[14] The resin sheet according to any one of [2] and

[10] to

[13] , wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer.

[15] The resin sheet according to any one of [2] and

[10] to

[14] , wherein the ratio of the content of the connected filler to the content of the flake filler in the resin sheet is 60 to 140 volume %.

[16] The resin sheet according to any one of [2] and

[10] to

[15] , wherein the flake-like filler has an average particle size of 5 μm or more. Effect of the Invention

[0012] According to the present invention, a novel resin sheet is provided that is capable of forming a new heat dissipation structure with a high heat dissipation effect. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view for illustrating a method for calculating an embedment rate R of a test piece using a resin sheet according to an embodiment of the present invention. FIG. [Diagram 2] 1 is a cross-sectional view showing a schematic example of a method of using a resin sheet according to an embodiment of the present invention. FIG. [Diagram 3] 5 is a cross-sectional view showing a schematic diagram of another example of a method of using the resin sheet according to the embodiment of the present invention. FIG. [Figure 4] FIG. 1 is a plan view showing the positions of resistors and thermocouples on a circuit board when checking the heat dissipation properties of a resin sheet or a test resin sheet against a heating element in Example 1, Comparative Examples 1-2, and Test Example 1. [Diagram 5] 4 is image data showing the results of confirming the heat dissipation properties of a resin sheet with respect to a heat generating body in Example 1. [Figure 6]13 is image data showing the results of confirming the heat dissipation properties of a resin sheet with respect to a heating element in Comparative Example 1. [Figure 7] 13 is image data showing the results of confirming the heat dissipation properties of a resin sheet with respect to a heating element in Comparative Example 2. [Figure 8] 1 shows image data showing the results of confirming the heat dissipation properties of a test resin sheet against a heat generating body in Test Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <<Resin sheet (first embodiment)>> The resin sheet of a first aspect according to one embodiment of the present invention includes a thermoplastic resin, a plate-like filler, and a connecting filler, the connecting filler having an average particle size of 2 μm or less, the resin sheet being one sheet or a laminate of two or more sheets of the resin sheet, and the resin sheet having a thickness of T 0 A test piece was used, and a pressure of 12 kPa was applied to the test piece in the thickness direction for 10 minutes in an environment of 100° C., and the thickness T 1 When the measurement was performed, the following formula: R=(T 0 -T 1 ) / T 0 ×100 The embedding rate R calculated by is 30% or more. The resin sheet of the first embodiment contains the plate-like filler and the connected filler, and therefore has high thermal conductivity and high heat dissipation in both the direction parallel to the surface and the thickness direction. Furthermore, the resin sheet of the first embodiment contains a thermoplastic resin, and the embedding ratio R is 30% or more, and has high flexibility when heated. By covering or preferably embedding a heat generating body such as a CPU (central processing unit) with the resin sheet of the first embodiment having such characteristics, a new heat dissipation structure can be configured in various electronic devices, and a high effect of suppressing heat generation in various electronic devices can be obtained. In addition, the heat dissipation structure can be configured not only for CPUs but also for other devices equipped with a heat generating body similar to the CPU, and a high effect of suppressing heat generation can be obtained. In this specification, the "direction parallel to the surface" may be referred to as the "plane direction", not only in the case of a resin sheet.

[0015] The resin sheet in the first embodiment has insulating properties.

[0016] <Thermoplastic resin> The resin sheet contains the thermoplastic resin, and thus can maintain a sheet-like shape and has conformability and adhesion to an object to which it is applied.

[0017] The thermoplastic resin is not particularly limited as long as it can impart flexibility to the resin sheet when heated and can achieve the embedment ratio R.

[0018] The resin sheet can be produced, for example, by molding (pressure-heat molding) a resin composition for producing the resin sheet, which will be described later. In this case, it is preferable that the thermoplastic resin has a melting point lower than the heating temperature (molding temperature) at which the resin composition is molded. By molding the resin composition at a temperature higher than the melting point of the thermoplastic resin, a resin sheet with higher uniformity can be obtained.

[0019] The melting point of the thermoplastic resin is preferably 90° C. or less, and may be, for example, either 80° C. or less or 70° C. or less. By using a thermoplastic resin having a melting point equal to or less than the upper limit, a resin sheet with higher uniformity can be obtained. The lower limit of the melting point of the thermoplastic resin is not particularly limited. For example, a thermoplastic resin having a melting point of 35° C. or higher is more easily available or produced. In one embodiment, the melting point of the thermoplastic resin may be, for example, any one of 35 to 90° C., 35 to 80° C., and 35 to 70° C. However, these are only examples of the melting point of the thermoplastic resin.

[0020] The melt flow rate (sometimes referred to as "MFR" in this specification) of the thermoplastic resin is preferably 1 to 40 g / 10 min, and may be, for example, any of 5 to 40 g / 10 min and 10 to 40 g / 10 min. When the MFR of the thermoplastic resin is equal to or greater than the lower limit, the resin sheet has a higher ability to conform to the object to which it is applied, and when covering a heating element with the resin sheet, for example, the heating element can be easily covered with the resin sheet. When the MFR of the thermoplastic resin is equal to or less than the upper limit, the shape of the resin sheet can be more stably maintained. In this specification, unless otherwise specified, MFR means a value measured in accordance with JIS K 6922-1.

[0021] A preferred example of the thermoplastic resin is ethylene-vinyl acetate copolymer (EVA). Ethylene-vinyl acetate copolymer has a lower melting point than other resins, and when heated, it exhibits a heat absorbing effect at or near its melting point, so that the resin sheet containing ethylene-vinyl acetate copolymer has higher heat dissipation properties due to its heat storage latent heat function. In addition, ethylene-vinyl acetate copolymer has flexibility, impact resistance, and adhesiveness, and when a heating element is covered with the resin sheet containing ethylene-vinyl acetate copolymer, the resin sheet easily adheres to the heating element. In addition, ethylene-vinyl acetate copolymer has polarity, so it can be composited with a flame retardant (e.g., magnesium hydroxide, etc.), and flame retardancy can be easily imparted to the resin sheet.

[0022] In the ethylene-vinyl acetate copolymer, the ratio of the amount (parts by mass) of the constituent units derived from vinyl acetate to the total amount (parts by mass) of the constituent units (sometimes referred to as the "vinyl acetate content" in this specification) is preferably 10 to 40% by mass, and may be, for example, either 20 to 40% by mass or 30 to 40% by mass. When the ratio (vinyl acetate content) is equal to or greater than the lower limit, the resin sheet has higher conformability and adhesion to the object to which it is applied. For example, when a heating element is covered with the resin sheet, the heating element can be easily covered with the resin sheet, and the resin sheet easily adheres to the heating element. When the ratio is equal to or less than the upper limit, the workability during production of the resin sheet is improved.

[0023] The resin sheet may contain only one type of thermoplastic resin, or may contain two or more types of resins. When the resin sheet contains two or more types of resins, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0024] The thermoplastic resin contained in the resin sheet is preferably an ethylene-vinyl acetate copolymer, since the effects of the present invention can be more significantly obtained.

[0025] In the resin sheet, the ratio of the content (parts by mass) of the thermoplastic resin to the total mass (parts by mass) of the resin sheet ([content (parts by mass) of thermoplastic resin in resin sheet)] / [total mass (parts by mass) of resin sheet)]×100) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. When the ratio is equal to or more than the lower limit, the effect obtained by the resin sheet containing the thermoplastic resin is further enhanced. In the resin sheet, the content (parts by mass) of the thermoplastic resin relative to the total mass (parts by mass) of the resin sheet is preferably 45% by mass or less, more preferably 40% by mass or less. When the content is equal to or less than the upper limit, the effect of the resin sheet containing components other than the thermoplastic resin is enhanced. In one embodiment, the ratio may be, for example, any one of 20 to 45 mass%, 25 to 45 mass%, and 30 to 45 mass%, or any one of 20 to 40 mass%, 25 to 40 mass%, and 30 to 40 mass%, although these are only examples of the ratio. The above ratio is usually the same as the ratio of the content (parts by mass) of the thermoplastic resin to the total content (parts by mass) of components that do not vaporize at room temperature in the resin composition described below ([content (parts by mass) of thermoplastic resin in resin composition)] / [total content (parts by mass) of components that do not vaporize at room temperature in resin composition)]×100).

[0026] In this specification, "room temperature" means a temperature that is neither particularly cooled nor heated, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0027] <Plate-shaped filler> The plate-like filler in the resin sheet is likely to be oriented in the same direction as the surface direction of the resin sheet or in a direction close to the surface direction of the resin sheet, and therefore the thermal conductivity of the resin sheet in the surface direction is particularly high, and the heat dissipation in the surface direction is high. For example, when a filler other than a plate-like filler, such as a polyhedral filler or a card-house-like filler (a filler in which plate-like fillers are aggregated to form secondary particles), is used instead of the plate-like filler, the heat dissipation property of the resin sheet in the surface direction is reduced. Furthermore, the card-house-like filler significantly reduces the flexibility of the resin sheet when heated.

[0028] The aspect ratio of the plate-like filler ([particle diameter of plate-like filler] / [thickness of plate-like filler]) is preferably 10 to 50, and may be, for example, any of 10 to 30 and 30 to 50. When the aspect ratio of the plate-like filler is within such a range, the effect obtained by the resin sheet containing the plate-like filler is further enhanced.

[0029] As the particle diameter of the flake-like filler, for example, the maximum length of a line segment connecting two different points on the periphery of the flake-like filler can be used. As the thickness of the flake-like filler, for example, the maximum distance between the main faces of the flake-like filler can be adopted. As the aspect ratio of the flake-like filler, for example, the average value of the aspect ratios of 50 randomly selected flake-like fillers can be used.

[0030] The average particle size of the plate-like filler is preferably 5 μm or more, and may be, for example, any one of 6.5 μm or more and 8 μm or more. When the average particle size of the plate-like filler is equal to or more than the lower limit, the effect obtained by using the plate-like filler is further enhanced. The upper limit of the average particle size of the flake-like filler is not particularly limited. For example, flake-like fillers having an average particle size of 15 μm or less are more readily available. In one embodiment, the average particle size of the flake-like filler may be, for example, any one of 5 to 15 μm, 6.5 to 15 μm, and 8 to 15 μm, although these are just examples of the average particle size of the flake-like filler.

[0031] In this specification, the term "average particle size", unless otherwise specified, refers to the particle size at 50% accumulation (D50) of the particles when the particle size distribution of the particles is measured on a volume basis by a laser diffraction particle size distribution measurement method, not limited to the case of a plate-like filler.

[0032] The thermal conductivity of the flake-like filler may be, for example, any one of 5 W / m·K or more, 10 W / m·K or more, 25 W / m·K or more, and 40 W / m·K or more. The upper limit of the thermal conductivity of the platy filler is not particularly limited. For example, platy fillers with a thermal conductivity of 400 W / m·K or less are more readily available. In one embodiment, the thermal conductivity of the flake-like filler may be, for example, any one of 5 to 400 W / m·K, 10 to 400 W / m·K, 25 to 400 W / m·K, and 40 to 400 W / m·K. However, these are just examples of the thermal conductivity of the flake-like filler.

[0033] The thermal conductivity of a filler, including a plate-like filler, can be measured, for example, by preparing a sintered body of the filler and measuring it using a known thermal conductivity measuring device such as a laser flash method or a hot disk method, or by measuring it using a thermal property microscope or the like.

[0034] In order to more easily lower the relative dielectric constant of the resin sheet described below, the relative dielectric constant of the flake-like filler is preferably 5.5 or less, and more preferably 4.5 or less. On the other hand, the lower limit of the relative dielectric constant of the flake-like filler is not particularly limited. For example, flake-like filler having a relative dielectric constant of 3.5 or more can be more easily prepared or obtained.

[0035] Examples of the material for the plate-like filler include metal nitrides such as boron nitride, and metal oxides such as aluminum oxide.

[0036] The resin sheet may contain only one type of flake-like filler, or may contain two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0037] The plate-like filler is boron nitride (BN) or aluminum oxide (Al 2 O 3 ) (i.e., boron nitride filler or aluminum oxide filler). A resin sheet containing such a plate-like filler has high heat dissipation properties, as well as better fluidity when heated and higher conformability to an object to which the resin sheet is applied. For example, when a heat generating element is covered with the resin sheet, the heat generating element can be easily covered with the resin sheet.

[0038] It is more preferable that the plate-like filler is made of boron nitride (BN) (i.e., a boron nitride filler). A resin sheet containing such a plate-like filler has the above-mentioned preferable properties, and further has further preferable properties as described below, since the relative dielectric constant is lowered.

[0039] In the resin sheet, the ratio of the content (volume part) of the plate-like filler to the total volume (volume part) of the resin sheet ([content (volume part) of the plate-like filler in the resin sheet)] / [total volume (volume part) of the resin sheet)]×100) is preferably 10 volume% or more, and may be, for example, 15 volume% or more, 20 volume% or more, or 25 volume% or more. When the ratio is equal to or more than the lower limit, the effect obtained by using the plate-like filler is further enhanced. In the resin sheet, the content (volume part) of the plate-like filler relative to the total volume (volume part) of the resin sheet is preferably 35% by volume or less, and may be, for example, any one of 30% by volume or less, 25% by volume or less, and 20% by volume or less. When the content is equal to or less than the upper limit, the effect obtained by using a filler other than the plate-like filler, such as the linked filler, becomes higher. In one embodiment, the ratio may be, for example, any of 10 to 35 volume%, 15 to 35 volume%, 20 to 35 volume%, and 25 to 35 volume%, any of 10 to 30 volume%, 15 to 30 volume%, 20 to 30 volume%, and 25 to 30 volume%, any of 10 to 25 volume%, 15 to 25 volume%, and 20 to 25 volume%, or 10 to 20 volume%, although these are only examples of the ratio.

[0040] <Connected filler> The resin sheet has high heat dissipation properties due to the inclusion of the connecting filler. The connecting filler in the resin sheet is widely distributed in both the surface direction and the thickness direction of the resin sheet, and as described later, the size of the connecting filler is small. Therefore, the connecting filler maintains contact with the plate-like filler in both the surface direction and the thickness direction of the resin sheet, thereby connecting the plate-like fillers to each other through itself. As a result, the thermal conductivity is increased in both the surface direction and the thickness direction of the resin sheet, and the heat dissipation properties are improved. In particular, the resin sheet has high thermal conductivity in the thickness direction due to the inclusion of the connecting filler, and the heat dissipation properties are improved. If the resin sheet does not contain the connecting filler, the heat dissipation properties in the thickness direction of the resin sheet will not be so high.

[0041] The average particle size of the connecting filler is 2 μm or less, which allows the flake-like fillers to be sufficiently connected to each other by the connecting filler. In order to enhance such effects, the average particle size of the linked filler is preferably 1.5 μm or less, and may be, for example, any one of 1.2 μm or less and 0.9 μm or less. The lower limit of the average particle size of the linked filler is not particularly limited. For example, linked fillers having an average particle size of 0.5 μm or more are more easily available, and the use of such linked fillers makes it easier to improve the heat dissipation properties of the resin sheet. In one embodiment, the average particle size of the linked filler may be, for example, any one of 0.5 to 2 μm, 0.5 to 1.5 μm, 0.5 to 1.2 μm, and 0.5 to 0.9 μm, although these are only examples of the average particle size of the linked filler.

[0042] The shape of the connecting filler is not particularly limited, but is preferably a shape having a plane, and more preferably a plate-like shape. When the connecting filler has a plane, particularly when it is plate-like, the contact area between the connecting filler and the plate-like filler becomes larger. As described above, the surface direction of the plate-like filler is likely to be oriented in the same direction as the surface direction of the resin sheet or in a direction close to the surface direction of the resin sheet, so even if the connecting filler has a plane, the contact area between the connecting filler and the plate-like filler tends to become smaller as the overall shape of the connecting filler deviates from the plate shape. However, when the average particle size of the connecting filler is 2 μm or less, sufficient contact between the connecting filler and the plate-like filler is maintained.

[0043] The linked filler is preferably non-aggregated (not aggregated). The lower the content of the linked filler, which is an aggregate, in the resin sheet, the more the fluidity of the resin sheet when heated is improved, and the more the resin sheet conforms to the object to which it is applied. For example, when a heating element is covered with the resin sheet, the heating element can be easily covered with the resin sheet.

[0044] The thermal conductivity of the connecting filler may be, for example, any one of 5 W / m·K or more, 10 W / m·K or more, 25 W / m·K or more, and 40 W / m·K or more. The upper limit of the thermal conductivity of the connecting filler is not particularly limited. For example, connecting fillers with a thermal conductivity of 400 W / m·K or less are more readily available. In one embodiment, the thermal conductivity of the connecting filler may be, for example, any one of 5 to 400 W / m·K, 10 to 400 W / m·K, 25 to 400 W / m·K, and 40 to 400 W / m·K. However, these are only examples of the thermal conductivity of the connecting filler.

[0045] Examples of the material of the connecting filler include metal hydroxides such as magnesium hydroxide.

[0046] The surface of the linked filler may or may not be treated with a surface treatment agent. By using a surface-treated linked filler, for example, the affinity between the linked filler and a resin such as a thermoplastic resin is improved, and the fluidity of the resin sheet is improved, so that the conformability and adhesion of the resin sheet to the object to which it is applied are improved. Examples of surface treatments for the interlocking filler include surface treatments with fatty acids or organosilicon compounds (silane coupling agents).

[0047] The resin sheet may contain only one type of connecting filler, or may contain two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0048] The connecting filler is magnesium hydroxide (Mg(OH) 2 ) (i.e., magnesium hydroxide filler). Since magnesium hydroxide is also a flame retardant, a resin sheet containing such a connecting filler has high flame retardancy in addition to high heat dissipation properties.

[0049] The resin sheet to which flame retardancy has been imparted, such as the resin sheet containing magnesium hydroxide filler, can meet, for example, grades V-0, V-1, or V-2 of the UL94 standard.

[0050] In the resin sheet, the ratio of the connected filler content to the plate-like filler content ([connected filler content in resin sheet (volume part)] / [plate-like filler content in resin sheet (volume part)]×100) is preferably 60 volume% or more, and may be, for example, any one of 65 volume% or more, 70 volume% or more, 90 volume% or more, and 200 volume% or more. When the ratio is equal to or more than the lower limit, the effect obtained by using the connected filler is further enhanced. In the resin sheet, the ratio of the content of the connected filler to the content of the plate-like filler is preferably 300% by volume or less, and may be, for example, any one of 250% by volume or less, 140% by volume or less, 110% by volume or less, and 80% by volume or less. When the ratio is equal to or less than the upper limit, the effect obtained by using a filler other than the connected filler, such as the plate-like filler, becomes higher. In one embodiment, the ratio is preferably 60 to 300 volume%, and may be, for example, any of 65 to 300 volume%, 70 to 300 volume%, 90 to 300 volume%, and 200 to 300 volume%, any of 60 to 250 volume%, 65 to 250 volume%, 70 to 250 volume%, and 90 to 250 volume%, any of 60 to 140 volume%, 65 to 140 volume%, 70 to 140 volume%, and 90 to 140 volume%, any of 60 to 110 volume%, 65 to 110 volume%, 70 to 110 volume%, and 90 to 110 volume%, or any of 60 to 80 volume%, 65 to 80 volume%, and 70 to 80 volume%. However, these are just examples of the ratio.

[0051] In the resin sheet, the ratio of the connected filler content (volume parts) to the total volume (volume parts) of the resin sheet ([connected filler content (volume parts) of resin sheet)] / [total volume (volume parts) of resin sheet)]×100) is preferably a numerical range that satisfies the ratio of the connected filler content to the plate-like filler content described above, and is, for example, preferably 6 volume% or more, and may be, for example, any one of 9.8 volume% or more, 14 volume% or more, 20 volume% or more, and 25 volume% or more. When the ratio is equal to or more than the lower limit, the effect obtained by using the connected filler is further enhanced. In the resin sheet, the content (volume part) of the connected filler relative to the total volume (volume part) of the resin sheet is preferably 49% by volume or less, and may be, for example, 33% by volume or less or 21% by volume or less. When the content is equal to or less than the upper limit, the effect obtained by using a filler other than the connected filler, such as the plate-like filler, becomes higher. In one embodiment, the ratio may be, for example, any one of 6 to 49 volume%, 9.8 to 49 volume%, 14 to 49 volume%, 20 to 49 volume%, and 25 to 49 volume%, any one of 6 to 33 volume%, 9.8 to 33 volume%, 14 to 33 volume%, and 20 to 33 volume%, and any one of 6 to 21 volume%, 9.8 to 21 volume%, and 14 to 21 volume%, but these are just examples of the ratio.

[0052] <Other ingredients> The resin sheet may contain other components that do not fall under any of the thermoplastic resin, the plate-like filler, and the connecting filler, as long as the effects of the present invention are not impaired. The other components can be arbitrarily selected depending on the purpose and are not particularly limited.

[0053] The resin sheet may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio thereof can be arbitrarily selected depending on the purpose.

[0054] Examples of the other components include additives known in the art. Examples of the additives include antioxidants, antistatic agents, viscosity reducers, thickeners, infrared absorbers, ultraviolet absorbers, and antiblocking agents.

[0055] In the resin sheet, the ratio of the total content (parts by mass) of the thermoplastic resin, the plate-like filler, and the connected filler to the total mass (parts by mass) of the resin sheet (([content of thermoplastic resin in resin sheet (parts by mass)] + [content of plate-like filler in resin sheet (parts by mass)] + [content of connected filler in resin sheet (parts by mass)]) / [total mass of resin sheet (parts by mass)] × 100) is preferably 80 mass% or more, more preferably 90 mass% or more, and may be, for example, any one of 95 mass% or more, 97 mass% or more, and 99 mass% or more. When the ratio is equal to or more than the lower limit, the heat dissipation property and flexibility when heated of the resin sheet are well balanced and higher. On the other hand, the ratio is 100 mass% or less. The above ratio is usually the same as the ratio of the total content (parts by mass) of the thermoplastic resin, the plate-like filler, and the connected filler to the total content (parts by mass) of components that do not vaporize at room temperature in the resin composition described below (([content (parts by mass) of thermoplastic resin in resin composition)] + [content (parts by mass) of plate-like filler in resin composition)] + [content (parts by mass) of connected filler in resin composition)]) / [total content (parts by mass) of components that do not vaporize at room temperature in resin composition)] × 100).

[0056] The thickness of the resin sheet is preferably 100 μm or more, and may be, for example, any one of 300 μm or more, 500 μm or more, 800 μm or more, and 1100 μm or more. When the thickness of the resin sheet is the lower limit or more, the heat dissipation property of the resin sheet is further improved. On the other hand, the thickness of the resin sheet is preferably 2000 μm or less, and may be, for example, either 1500 μm or less or 1000 μm or less. When the thickness of the resin sheet is equal to or less than the upper limit, the flexibility of the resin sheet when heated is increased. In one embodiment, the resin sheet may have a thickness of, for example, any one of 100 to 2000 μm, 300 to 1500 μm, 500 to 1000 μm, and 800 to 1500 μm, although these are only examples of the thickness of the resin sheet. The thickness of the resin sheet is preferably adjusted according to the thickness of the object to which the resin sheet is to be applied, as described below.

[0057] <Characteristics of resin sheets> [Embedding rate R] The resin sheet has a thickness of T 0 or a laminate of two or more of the resin sheets, and the thickness of the laminate is T 0 A test piece of the above was used, and a pressure of 12 kPa was applied to the test piece in the thickness direction for 10 minutes in an environment of 100° C., and the thickness T 1 When the measurement was performed, the following formula: R=(T 0 -T 1 ) / T 0 ×100 The embedding ratio R calculated by is 30% or more. The resin sheet of the first aspect having the embedding ratio R in this range has high flexibility when heated. Therefore, the heat generating element can be well covered by the resin sheet. Hereinafter, the method of calculating the embedding rate R will be described in more detail with reference to the drawings.

[0058] FIG. 1 is a cross-sectional view for illustrating a method for calculating the embedment rate R of the test piece using the resin sheet. In addition, the figures used in the following explanation may show enlarged key parts for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as the actual ones.

[0059] For example, T 1 In order to measure the thickness of the test piece at the pressurized portion after heating and pressing, as shown in Fig. 1(a), the test piece 10 is placed on a flat surface, and an indentation material 9 is placed near the center of one surface 10a, which is the upward exposed surface of the test piece 10. The indentation material 9 is a means for contacting the test piece 10 and applying pressure to indent the test piece 10. The test piece 10 is either one of the resin sheets or a laminate of two or more of the resin sheets. Regardless of whether the test piece 10 is one of these, the thickness of the test piece 10 in the thickness direction of the test piece 10 when no pressure is applied to the test piece 10 is T 0 It is. T 0 is not particularly limited, and may be, for example, any of 500 μm or more, 1000 μm or more, and 1500 μm or more, and may be any of 3500 μm or less, 3000 μm or less, and 2500 μm or less.

[0060] In Fig. 1, the contents of the test piece 10 (resin sheet) are omitted. In Fig. 2 and subsequent figures, the contents of the resin sheet are also omitted in the cross-sectional views of the resin sheet of this embodiment.

[0061] The material of the indentation member 9 is not particularly limited as long as it is hard, and examples thereof include various ceramics. The shape of the indentation material 9 is not particularly limited as long as the contact portion with the test piece 10 is flat, and may be, for example, any of a rectangular column, a truncated pyramid, a cylindrical column, a truncated cone, an elliptical column, an elliptical truncated column, etc. The area of ​​the contact surface (in other words, the indentation surface) 9b of the indentation material 9 with the test piece 10 may be smaller than the area of ​​one surface 10a of the test piece 10, but it is preferable that the area be 0.05 to 0.30 times the area of ​​the one surface 10a of the test piece 10.

[0062] Next, the weight 8 is placed on the other surface 9a of the indentation member 9 in this state (the exposed surface facing upward that is not in contact with one surface 10a of the test piece 10). The weight 8 may be placed on a partial area of ​​the other surface 9a of the pressing member 9, or on the entire surface. The number of weights 8 placed on the pushing member 9 may be one or two or more. In this way, by placing weight 8 on the indentation material 9 and stacking the test piece 10, indentation material 9 and weight 8 in this order to form laminate 100, a pressure of 12 kPa is applied to the test piece 10 in its thickness direction by the indentation material 9 and weight 8.

[0063] Next, the laminate 100 in this state is immediately placed in an environment at 100° C. and left to stand for 10 minutes. As described above, a pressure of 12 kPa is applied to the test piece 10 in the thickness direction of the test piece 10 in an environment of 100° C. for 10 minutes. When the laminate 100 is placed in an environment of 100° C., the heated test piece 10 softens and is pressed into the indentation material 9, causing the contact portion of the test piece 10 with the indentation material 9 to dent. Next, after 10 minutes, the thickness T of the test piece 10 at the portion of the laminate 100 being heated and pressed was measured. 1 Measure.

[0064] Therefore, T 0 and T 1 These measured values ​​are used to calculate the embedment rate R of the test piece 10 according to the above formula.

[0065] In order to allow the heat generating element to be easily covered with the resin sheet, the embedment rate R is preferably 35% or more, and may be, for example, any one of 40% or more, 45% or more, and 50% or more. On the other hand, there is no particular upper limit to the embedment rate R. For example, a resin sheet having an embedment rate R of 65% or less or 60% or less can be manufactured more easily. In one embodiment, the embedding rate R may be, for example, any one of 30 to 65%, 35 to 65%, 40 to 65%, 45% to 65%, and 50 to 65%, or any one of 30 to 60%, 35 to 60%, 40 to 60%, and 45 to 60%. However, these are just examples of the embedding rate R.

[0066] The embedment rate R of the resin sheet can be adjusted, for example, by adjusting the type and content of the components contained in the resin sheet, in particular, the type and content of the thermoplastic resin.

[0067] [Thermal conductivity in the plane direction] The thermal conductivity of the resin sheet in the plane direction is preferably 2 W / m K or more, more preferably 3 W / m K or more, and may be, for example, 4 W / m K or more. The resin sheet having a thermal conductivity equal to or more than the lower limit has high heat dissipation properties in the plane direction. The upper limit of the thermal conductivity in the plane direction of the resin sheet is not particularly limited. For example, a resin sheet having a thermal conductivity of 15 W / m·K or less can be more easily manufactured. In one embodiment, the thermal conductivity of the resin sheet in the planar direction may be, for example, any one of 2 to 15 W / m·K, 3 to 15 W / m·K, and 4 to 15 W / m·K. Not limited to the above-mentioned resin sheet, the thermal conductivity in the plane direction of a resin sheet is, more specifically, the thermal conductivity of the resin sheet in a direction parallel to one surface or the other surface of the resin sheet.

[0068] The thermal conductivity in the planar direction of the resin sheet can be measured by a hot disk method in accordance with ISO 22007-2, for example, using a hot disk method thermal property measuring device (e.g., "TPS 2500 S", "TPS 500 S", etc.) manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0069] The thermal conductivity in the planar direction of the resin sheet can be adjusted, for example, by adjusting the type of thermoplastic resin and its content in the resin sheet; the type of the plate-like filler and its content in the resin sheet; the type of the connecting filler and its content in the resin sheet; the thickness of the resin sheet, etc.

[0070] [Dielectric constant] The relative dielectric constant of the resin sheet at a frequency of 10 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is preferably 4 or less, and may be, for example, any one of 3.75 or less, 3.65 or less, and 3.55 or less. The resin sheet having a relative dielectric constant at a frequency of 10 GHz or less has high insulation properties and is particularly suitable for mounting by covering a heating element on a circuit board, for example, in that it is highly effective in suppressing the generation of noise in electrical signals in a circuit in an object to which the resin sheet is mounted. The lower limit of the relative dielectric constant at a frequency of 10 GHz is not particularly limited. For example, the resin sheet having a relative dielectric constant of 1 or more at a frequency of 10 GHz can be more easily manufactured. In one embodiment, the relative dielectric constant at a frequency of 10 GHz may be, for example, any one of 1 to 4, 1 to 3.75, 1 to 3.65, and 1 to 3.55, although these are only examples of the relative dielectric constant at a frequency of 10 GHz. The relative dielectric constant at a frequency of 10 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0071] The relative dielectric constant of the resin sheet at a frequency of 1 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is preferably 4 or less, and may be, for example, either 3.9 or less or 3.8 or less. The resin sheet having a relative dielectric constant at a frequency of 1 GHz or less has high insulation properties and is particularly suitable for mounting by covering a heating element on a circuit board, for example, in that it is highly effective in suppressing the generation of noise in electrical signals in a circuit in an object to which the resin sheet is mounted. The lower limit of the relative dielectric constant at a frequency of 1 GHz is not particularly limited. For example, the resin sheet having a relative dielectric constant of 1 or more at a frequency of 1 GHz can be more easily manufactured. In one embodiment, the relative dielectric constant at a frequency of 1 GHz may be, for example, any one of 1 to 4, 1 to 3.9, and 1 to 3.8, although these are merely examples of the relative dielectric constant at a frequency of 1 GHz. The relative dielectric constant at a frequency of 1 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0072] The relative dielectric constant of the resin sheet can be adjusted by adjusting the types and contents of the components contained in the resin sheet, regardless of the frequency.

[0073] [Dissipation factor] The dielectric loss tangent of the resin sheet at a frequency of 10 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is preferably 0.01 or less, and may be, for example, any one of 0.0065 or less, 0.0055 or less, and 0.0045 or less. The resin sheet having a dielectric loss tangent at a frequency of 10 GHz in such a range has high radio wave transmittance and is suitable for constituting an electronic device equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 10 GHz is not particularly limited. For example, the resin sheet having a dielectric loss tangent of 0.001 or more at a frequency of 10 GHz can be more easily manufactured. In one embodiment, the dielectric loss tangent at a frequency of 10 GHz may be, for example, any one of 0.001 to 0.01, 0.001 to 0.0065, 0.001 to 0.0055, and 0.001 to 0.0045, although these are only examples of the dielectric loss tangent at a frequency of 10 GHz. The dielectric loss tangent at a frequency of 10 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0074] The dielectric loss tangent of the resin sheet at a frequency of 1 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is preferably 0.01 or less, and may be, for example, 0.009 or less or 0.008 or less. The resin sheet having a dielectric loss tangent at a frequency of 1 GHz in such a range has high radio wave transmittance and is suitable for constituting an electronic device equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 1 GHz is not particularly limited. For example, the resin sheet having a dielectric loss tangent of 0.001 or more at a frequency of 1 GHz can be more easily manufactured. In one embodiment, the dielectric loss tangent at a frequency of 1 GHz may be, for example, any one of 0.001 to 0.01, 0.001 to 0.009, and 0.001 to 0.008, although these are merely examples of the dielectric loss tangent at a frequency of 1 GHz. The dielectric loss tangent at a frequency of 1 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0075] The dielectric loss tangent of the resin sheet can be adjusted by adjusting the types and contents of the components contained in the resin sheet, regardless of the frequency.

[0076] In the resin sheet, it is preferable that the relative dielectric constant at a frequency of 10 GHz and the relative dielectric constant at a frequency of 1 GHz are both within the above numerical ranges. In the resin sheet, it is preferable that the dielectric tangent at a frequency of 10 GHz and the dielectric tangent at a frequency of 1 GHz are both within the above numerical ranges. In the resin sheet, it is more preferable that the relative dielectric constant at a frequency of 10 GHz, the relative dielectric constant at a frequency of 1 GHz, the dielectric loss tangent at a frequency of 10 GHz, and the dielectric loss tangent at a frequency of 1 GHz are all within the above numerical ranges.

[0077] [density] The density of the resin sheet is 2 g / cm 3 It is preferable that the density is equal to or less than 1.7 g / cm. 3 Various electronic devices configured with such a resin sheet attached thereto are suitable for use in, for example, configuring portable electronic devices, since heat generation is suppressed and the electronic devices are lightweight. The lower limit of the density of the resin sheet is not particularly limited. 3 The resin sheet described above can be more easily realized. In one embodiment, the density of the resin sheet is, for example, 1 to 2 g / cm 3 , and 1 to 1.7 g / cm 3 However, these are just examples of the density of the resin sheet. The density of the resin sheet can be adjusted, for example, by adjusting the types and contents of the components contained in the resin sheet.

[0078] The density of the resin sheet can be measured by a known method, for example, in accordance with JIS K 7112:1999 or JIS K 0061:2022 (density gradient tube method).

[0079] The resin sheet may be irradiated with an electron beam. In this case, the resin sheet is preferably irradiated with an electron beam under conditions of an absorbed dose of 20 to 300 kGy. The acceleration voltage of the electron beam irradiation is preferably 100 to 300 kV. By irradiating the resin sheet with electron beams, the resin sheet is partially crosslinked, and the heat resistance and repairability of the resin sheet are improved.

[0080] <<Resin composition and method for producing same>> The resin sheet of the first embodiment can be produced, for example, by using a resin composition (sometimes referred to in this specification as the "resin composition of the first embodiment") containing the thermoplastic resin, the plate-like filler, the connecting filler, and, as necessary, the other components.

[0081] The resin composition may contain a solvent in addition to the above-mentioned components. The resin composition containing a solvent may have improved handleability. In this specification, unless otherwise specified, the term "solvent" refers not only to a component capable of dissolving a solute in a solution, but also to a component that serves as a dispersion medium in a dispersion liquid.

[0082] The solvent is preferably an organic solvent, and more preferably an organic solvent that can be removed by vaporization when the resin composition is heated.

[0083] The content of the solvent in the resin composition can be arbitrarily selected depending on the purpose, and is not particularly limited.

[0084] The resin composition may be produced by adjusting the type and content of the components contained so that the resin sheet contains the desired components (constituent materials) in the desired content. For example, the content ratio of the components that do not vaporize at room temperature in the resin composition is usually the same as the content ratio of the components in the resin sheet.

[0085] The resin composition can be produced by blending the thermoplastic resin, the flake-like filler, the connecting filler, and, if necessary, the other components, and, if necessary, the solvent. The order of addition of the components when blending is not particularly limited, and two or more components may be added simultaneously. The method for mixing the components during blending is not particularly limited, and may be appropriately selected from known methods. The temperature and time for adding and mixing each component are not particularly limited as long as each blended component does not deteriorate, and can be appropriately adjusted.

[0086] The resin composition may be, for example, a mixture obtained by kneading the thermoplastic resin, the flake-like filler, the connecting filler, and, if necessary, the other components.

[0087] <<Manufacturing method for resin sheets>> The resin sheet can be produced, for example, by molding the resin composition. The resin composition can be molded by a known method. For example, when molding under vacuum conditions, the resin composition can be molded by a vacuum hot press.

[0088] The molding temperature (pressurizing temperature) of the resin composition is preferably higher than the melting point of the thermoplastic resin, and may be, for example, any of a temperature 15° C. or higher than the melting point of the thermoplastic resin, a temperature 35° C. or higher than the melting point of the thermoplastic resin, and a temperature 55° C. or higher than the melting point of the thermoplastic resin. When the molding temperature is equal to or higher than the lower limit, a resin sheet with higher uniformity can be obtained. The upper limit of the molding temperature is not particularly limited. For example, if the molding temperature is equal to or lower than a temperature 75° C. higher than the melting point of the thermoplastic resin, excessive heating can be avoided.

[0089] The pressure during molding of the resin composition is not particularly limited as long as the effect of pressing is sufficiently obtained, but is preferably 3 MPa or more, and may be, for example, any one of 8 MPa or more and 13 MPa or more. By setting the pressure to the lower limit or more, a resin sheet with higher uniformity can be obtained. The upper limit of the pressure is not particularly limited. For example, if the pressure is 20 MPa or less, excessive pressurization can be avoided.

[0090] The molding time (pressurizing time) of the resin composition is not particularly limited as long as the effect of pressing is sufficiently obtained, and can be set arbitrarily according to the pressure during molding, for example, but is preferably 0.5 minutes or more. By setting the molding time to the lower limit or more, a resin sheet with higher uniformity can be obtained. The upper limit of the molding time is not particularly limited. For example, if the molding time is 10 minutes or less, excessive pressure can be avoided.

[0091] The molding of the resin composition is preferably carried out under reduced pressure, and more preferably under vacuum conditions, for example, a pressure of 0.05 MPa or less. By molding under reduced pressure in this manner, the resin sheet having higher uniformity can be obtained.

[0092] <<Resin sheet (second embodiment)>> A resin sheet of a second aspect according to one embodiment of the present invention includes a thermoplastic resin, a flake-like filler, and a connecting filler, and the connecting filler has an average particle size of 2 μm or less. The resin sheet of the second aspect contains the plate-like filler and the connected filler, and therefore has high thermal conductivity and high heat dissipation both in the direction parallel to the surface and in the thickness direction. Furthermore, the resin sheet of the second aspect contains a thermoplastic resin, and therefore has flexibility when heated. The resin sheet of the second embodiment may be the same as the resin sheet of the first embodiment, except that the embedment rate R is not specified to be 30% or more. By covering or preferably embedding a heat generating body such as a CPU with the resin sheet of the second aspect having such characteristics, a new heat dissipation structure can be configured in various electronic devices, and a high effect of suppressing heat generation in various electronic devices can be obtained. In addition, the heat dissipation structure can be configured not only for CPUs but also for other devices equipped with a heat generating body similar to the CPU, and a high effect of suppressing heat generation can be obtained.

[0093] The resin sheet in the second embodiment has insulating properties.

[0094] The resin sheet of the second embodiment may contain other components that do not fall under any of the thermoplastic resin, the plate-like filler, and the connecting filler, as long as the effects of the present invention are not impaired.

[0095] The thermoplastic resin, the plate-like filler, the connecting filler, and the other components contained in the resin sheet of the second embodiment may be the same as the thermoplastic resin, the plate-like filler, the connecting filler, and the other components contained in the resin sheet of the first embodiment described above. These components contained in the resin sheet of the second embodiment provide the same effects in the resin sheet of the second embodiment as in the resin sheet of the first embodiment.

[0096] The second embodiment of the resin sheet containing a thermoplastic resin, a plate-like filler, a connecting filler, and the other components may be the same as the first embodiment of the resin sheet containing a thermoplastic resin, a plate-like filler, a connecting filler, and the other components. More specifically, for example, it is as follows.

[0097] The thermoplastic resin, the plate-like filler, the connecting filler, and the other components contained in the resin sheet of the second embodiment may each be only one type, or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0098] The thermoplastic resin contained in the resin sheet of the second embodiment is preferably an ethylene-vinyl acetate copolymer for the same reasons as in the resin sheet of the first embodiment.

[0099] In the resin sheet of the second embodiment, the ratio of the content (parts by mass) of the thermoplastic resin to the total mass (parts by mass) of the resin sheet ([content (parts by mass) of thermoplastic resin in resin sheet)] / [total mass (parts by mass) of resin sheet)]×100) is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 20% by mass or more, and preferably 45% by mass or less, and may be, for example, 20 to 45% by mass, or may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0100] The plate-like filler contained in the resin sheet of the second embodiment is boron nitride (BN) or aluminum oxide (Al) for the same reason as in the case of the resin sheet of the first embodiment. 2 O 3 ), more preferably made of boron nitride (i.e., boron nitride filler).

[0101] The average particle size of the plate-like filler contained in the resin sheet of the second embodiment is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 5 μm or more, and may be 15 μm or less, for example, 5 to 15 μm, and may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0102] In the resin sheet of the second embodiment, the ratio of the content (volume part) of the plate-like filler to the total volume (volume part) of the resin sheet ([content (volume part) of the plate-like filler in the resin sheet)] / [total volume (volume part) of the resin sheet)]×100) is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 10 vol% or more, and preferably 35 vol% or less, and may be, for example, 10 to 35 vol%, or may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0103] The connecting filler contained in the resin sheet of the second embodiment is magnesium hydroxide (Mg(OH) 2 ) (i.e., magnesium hydroxide filler). The resin sheet of the second embodiment to which flame retardancy has been imparted, such as the resin sheet containing magnesium hydroxide filler, can meet, for example, grades V-0, V-1, or V-2 of the UL94 standard.

[0104] In the resin sheet of the second embodiment, the ratio of the content of connected filler to the content of plate-like filler ([content of connected filler in resin sheet (volume parts)] / [content of plate-like filler in resin sheet (volume parts)]×100) is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 60 vol% or more, and preferably 300 vol% or less, and may be 140 vol% or less, for example, any one of 60 to 300 vol% and 60 to 140 vol%, and may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0105] In the resin sheet of the second embodiment, the ratio of the content (volume part) of the connected filler to the total volume (volume part) of the resin sheet ([content (volume part) of the connected filler in the resin sheet)] / [total volume (volume part) of the resin sheet)]×100) is preferably a numerical range that satisfies the ratio of the content of the connected filler to the content of the plate-like filler described above, and for the same reasons as in the case of the resin sheet of the first embodiment, it is, for example, preferably 6 vol% or more and preferably 49 vol% or less, and may be, for example, 6 to 49 vol%, or may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0106] In the resin sheet of the second embodiment, the ratio of the total content (parts by mass) of the thermoplastic resin, the plate-like filler, and the connected filler to the total mass (parts by mass) of the resin sheet (([content of thermoplastic resin in resin sheet (parts by mass)] + [content of plate-like filler in resin sheet (parts by mass)] + [content of connected filler in resin sheet (parts by mass)]) / [total mass of resin sheet (parts by mass)] × 100) is preferably 80 mass% or more, and 100 mass% or less, for the same reasons as in the case of the resin sheet of the first embodiment.

[0107] The thickness of the resin sheet of the second embodiment is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 100 μm or more and preferably 2000 μm or less, and may be, for example, 100 to 2000 μm, or may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0108] The thermal conductivity in the plane direction of the resin sheet of the second embodiment is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 2 W / m·K or more, and may be 15 W / m·K or less, for example, 2 to 15 W / m·K, and may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0109] The relative dielectric constant of the resin sheet of the second embodiment at a frequency of 10 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 4 or less for the same reasons as in the case of the resin sheet of the first embodiment, and may be 1 or more, for example, 1 to 4, and may be in the same numerical range as in the case of the resin sheet of the first embodiment. In the second embodiment, the relative dielectric constant at a frequency of 10 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0110] The relative dielectric constant of the resin sheet of the second embodiment at a frequency of 1 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 4 or less for the same reasons as in the case of the resin sheet of the first embodiment, and may be 1 or more, for example, 1 to 4, and may be in the same numerical range as in the case of the resin sheet of the first embodiment. In the second embodiment, the relative dielectric constant at a frequency of 1 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0111] The dielectric tangent of the resin sheet of the second embodiment at a frequency of 10 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 0.01 or less, and may be 0.001 or more, for example, 0.001 to 0.01, and may be in the same numerical range as in the case of the resin sheet of the first embodiment. In the second embodiment, the dielectric loss tangent at a frequency of 10 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0112] The dielectric tangent of the resin sheet of the second embodiment at a frequency of 1 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 0.01 or less, and may be 0.001 or more, for example, 0.001 to 0.01, and may be in the same numerical range as in the case of the resin sheet of the first embodiment. In the second embodiment, the dielectric loss tangent at a frequency of 1 GHz is preferably a value measured at room temperature (for example, at a temperature of 23° C.).

[0113] In the resin sheet of the second embodiment, it is preferable that the relative dielectric constant at a frequency of 10 GHz and the relative dielectric constant at a frequency of 1 GHz are both within the above numerical ranges. In the resin sheet of the second embodiment, it is preferable that the dielectric loss tangent at a frequency of 10 GHz and the dielectric loss tangent at a frequency of 1 GHz are both within the above numerical ranges. In the resin sheet of the second embodiment, it is more preferable that the relative dielectric constant at a frequency of 10 GHz, the relative dielectric constant at a frequency of 1 GHz, the dielectric tangent at a frequency of 10 GHz, and the dielectric tangent at a frequency of 1 GHz are all within the above numerical ranges.

[0114] The density of the resin sheet of the second embodiment is set to 2 g / cm for the same reason as in the case of the resin sheet of the first embodiment. 3 It is preferable that the density is less than 1 g / cm 3 or more, for example, 1 to 2 g / cm 3 and may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0115] The relative dielectric constant, dielectric loss tangent and density of the resin sheet of the second embodiment can be adjusted, for example, by the same method as in the case of the resin sheet of the first embodiment, and can be measured by the same method as in the case of the resin sheet of the first embodiment.

[0116] The flexibility of the resin sheet of the second embodiment when heated can be adjusted more easily by adjusting, for example, the type and content of the components contained in the resin sheet, particularly the type and content of the thermoplastic resin. In this way, by adjusting the type and content of the components contained in the resin sheet of the second embodiment, the resin sheet of the second embodiment can be given the flexibility when heated similar to that of the resin sheet of the first embodiment in which the embedment ratio R is specified to 30% or more.

[0117] The resin sheet of the second embodiment may be irradiated with an electron beam for the same reasons as in the case of the resin sheet of the first embodiment, and is preferably irradiated with an electron beam at an absorbed dose of 20 to 300 kGy, and the accelerating voltage of the electron beam irradiation is preferably 100 to 300 kV.

[0118] The resin sheet of the second embodiment can be produced, for example, by using a resin composition (sometimes referred to in this specification as the "resin composition of the second embodiment") containing the thermoplastic resin, the plate-like filler, the connecting filler, and, as necessary, the other components. The resin composition of the second embodiment is the same as the resin composition for producing the resin sheet of the first embodiment described above (the resin composition of the first embodiment), except that either or both of the types and amounts of the blended components may be different. For example, the resin composition of the second embodiment may contain a solvent, and examples of the solvent include the same solvents as those that may be contained in the resin composition of the first embodiment.

[0119] The resin composition of the second embodiment can be produced in the same manner as the resin composition of the first embodiment, except that either or both of the types and amounts of the blended components may be different.

[0120] The resin sheet of the second embodiment can be produced in the same manner as the resin sheet of the first embodiment described above, except that the resin composition of the second embodiment is used instead of the resin composition of the first embodiment. For example, the molding temperature (pressurizing temperature) of the resin composition of the second embodiment is preferably higher than the melting point of the thermoplastic resin for the same reasons as in the case of the resin sheet of the first embodiment, and may be a temperature 15°C or more higher than the melting point of the thermoplastic resin, or may be equal to or lower than a temperature 75°C higher than the melting point of the thermoplastic resin, or may be in the same numerical range as in the case of the resin sheet of the first embodiment.

[0121] <<Method of Using the Resin Sheet of the First Aspect and the Resin Sheet of the Second Aspect>> By using the resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment) to cover the surface of a heat generating body such as a CPU, a new heat dissipation structure can be formed in various electronic devices, and heat generation in the various electronic devices can be suppressed.

[0122] <How to use 1> 2 is a cross-sectional view showing a schematic example of a method of using the resin sheet (sometimes referred to as "method of use 1" in this specification). Here, an example is shown in which the resin sheet covers the entire exposed surface of the heating element, i.e., the heating element is embedded.

[0123] In FIG. 2 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.

[0124] In method of use 1, first, as shown in FIG. 2(a), a laminated structure 101 is prepared in which a resin sheet 1, a heat spreader 4, and a housing 3 are laminated in this order in the thickness direction. The resin sheet 1 is the resin sheet of this embodiment described above (the resin sheet of the first aspect or the resin sheet of the second aspect). The housing 3 is a known material and can be selected arbitrarily depending on the purpose. Examples of materials for the housing 3 include resin, metal, and carbon materials. The heat spreader 4 is also known, and examples of the material thereof include metals such as copper, and carbon materials such as graphite.

[0125] The circuit board 7 is not particularly limited and may be a known one. A heating element 5 such as a CPU is provided on one surface 7a of the circuit board 7 via a connection portion 6.

[0126] Resin sheet 1 thickness T x is preferably in the range of values ​​described above. On the other hand, the thickness T of the resin sheet 1 x is preferably 0.5 to 1.5 times, more preferably 0.6 to 1.3 times, and may be, for example, 0.6 to 1 times the height (thickness) of the object to which it is applied. x When T is equal to or greater than the lower limit, the object to which the resin sheet 1 is applied can be covered more easily. x By making T equal to or less than the upper limit, it is possible to prevent the thickness of the resin sheet 1 from becoming excessive. Since the resin sheet 1 has high flexibility when heated, when the resin sheet 1 is pressed against an object to which it is applied, an area of ​​the resin sheet 1 that is pushed aside by the object to which it is applied is generated, and this area can contribute to maintaining the thickness of the resin sheet 1. xHowever, even if the resin sheet 1 is less than one time the height (thickness) of the object to which the application is applied, the object can be sufficiently embedded in the resin sheet 1. Resin sheet 1 thickness T x It is preferable that the numerical range described above is satisfied, and also the numerical range based on the height of the object to which the present invention is applied is satisfied. When the height (thickness) of the application object is not constant, the height at the highest part (the thickness at the thickest part) is regarded as the height (thickness) of the application object.

[0127] Here, the object to which the resin sheet 1 is applied is, for example, the heating element 5 and the connection part 6 when the resin sheet 1 covers the entire exposed surface of the heating element 5 and the entire exposed part of the connection part 6, and the height of the heating element 5 and the connection part 6 is indicated by the symbol T y In contrast to this, for example, when the resin sheet 1 covers the entire exposed surface of the heating element 5 and does not cover the connection portion 6, the application target of the resin sheet 1 is the entire area of ​​the heating element 5. For example, when the resin sheet 1 covers only a portion of the exposed surface of the heating element 5, the application target of the resin sheet 1 is the area of ​​the heating element 5 that corresponds to this portion of the exposed surface.

[0128] The laminated structure 101 is disposed in the vicinity of the heat generating element 5 with the resin sheet 1 facing the heat generating element 5 (in other words, the housing 3 facing the opposite side to the heat generating element 5). That is, one surface 1a of the resin sheet 1 and the exposed surface 5a of the heat generating element 5 are opposed to each other.

[0129] In the first method of use, the laminated structure 101 is then 1 3, in the direction of arrow P, so as to press the resin sheet 1 against the heating element 5, or to move the heating element 5 on the circuit board 7 together with the circuit board 7 in the direction of arrow P. 2 3, the heat generating element 5 is pressed against the resin sheet 1, or the laminated structure 101 is moved in the direction of the arrow P 1 1, the heating element 5 on the circuit board 7 is moved in the direction of the arrow P together with the circuit board 7. 22(b), the resin sheet 1 is moved in the direction of the arrows to press the resin sheet 1 against the heating element 5. As a result, the heating element 5 is covered with the resin sheet 1, as shown in FIG. 2(b). At this time, a partial area of ​​one surface 1a of the resin sheet 1 is brought into contact with the upper surface of the exposed surface 5a of the heating element 5 that faces the resin sheet 1, and further, another area of ​​the one surface 1a of the resin sheet 1 is brought into contact with one surface 7a of the circuit board 7 or is brought close to the one surface 7a of the circuit board 7. As a result, the resin sheet 1 covers the entire exposed surface 5a of the heating element 5 (all areas including the upper surface and side surfaces), and the heating element 5 is embedded.

[0130] 2(b) shows a state in which one heating element 5 is provided on one surface 7a of the circuit board 7, the number of heating elements provided on one surface 7a of the circuit board 7 may be only one, or may be two or more. When there are two or more heating elements provided on one surface 7a of the circuit board 7, these two or more heating elements may be the same as each other or different. In other words, the two or more heating elements may all be the same, all be different, or only some may be the same.

[0131] When there are two or more heating elements provided on one surface 7a of the circuit board 7 and these two or more heating elements are to be covered integrally by a single resin sheet 1, as described above, all of the heating elements can be easily and sufficiently covered by the single resin sheet 1 by bringing other areas of the one surface 1a of the resin sheet 1 into contact with the one surface 7a of the circuit board 7 or close to the one surface 7a of the circuit board 7.

[0132] When there are two or more heating elements provided on one surface 7a of circuit board 7, at least some of the heating elements may be covered by two or more resin sheets 1 separately rather than integrally.

[0133] When covering the heating element 5 with the resin sheet 1 (embedding the heating element 5 in FIG. 2), it is preferable to adjust the temperature of the target heating element 5 to, for example, a temperature similar to the molding temperature (pressurizing temperature) of the resin composition (temperature based on the melting point of the thermoplastic resin) as described above. By adjusting the temperature of the heating element 5 in this manner, the heating element 5 can be covered more uniformly with the resin sheet 1, the heat dissipation properties of the resin sheet 1 are improved, and the heat dissipation efficiency of the heating element 5 is improved. The temperature of the heating element 5 can be adjusted using a known temperature adjustment means such as an oven.

[0134] When covering the heating element 5 with the resin sheet 1 (embedding in FIG. 2), the pressure applied to the resin sheet 1 when pressing the resin sheet 1 against the heating element 5, and the pressure applied to the heating element 5 (more specifically, the circuit board 7) when pressing the heating element 5 against the resin sheet 1, are preferably 10 to 20 kPa. When the pressure is equal to or greater than the lower limit, the heating element 5 can be covered more uniformly with the resin sheet 1. When the pressure is equal to or less than the upper limit, excessive pressure can be avoided. Since the resin sheet 1 has high flexibility when heated, it can adequately cover the heating element 5 even with a low pressure of about 10 to 20 kPa.

[0135] In this state where the heating element 5 is covered with the resin sheet 1, the resin sheet 1 has high flexibility when heated, so that there is high adhesion between the resin sheet 1 and the heating element 5, and there is high adhesion between the resin sheet 1 and the connection portion 6. More specifically, the occurrence of gaps is suppressed between one surface 1a of the resin sheet 1 and the exposed surface 5a of the heating element 5, and between one surface 1a of the resin sheet 1 and the connection portion 6, and it is also possible to eliminate the existence of such gaps (to completely prevent the occurrence of such gaps) by adjusting the conditions when the heating element 5 is covered with the resin sheet 1.

[0136] In this state where the heat generating element 5 is covered with the resin sheet 1, the heat generated by the heat generating element 5 is radiated in the resin sheet 1 in the planar direction D S , and is dissipated, for example, into the atmosphere. The heat generated by the heating element 5 is dissipated in the resin sheet 1 in the thickness direction D TThe heat is conducted along the thickness direction D and dissipated to the air through the heat spreader 4. At this time, since the heat generating element 5 is embedded in the resin sheet 1, the distance between the heat generating element 5 and the heat spreader 4 is shorter than when the heat generating element 5 is not embedded. T Further, the heat dissipation in the thickness direction D of the resin sheet 1 is improved. T The heat conducted along the wiring may be dissipated into the atmosphere via the circuit board 7. When the housing 3 is made of a material having high thermal conductivity such as a metal or a carbon material, the thickness direction D of the resin sheet 1 T The heat conducted along the heat spreader 4 is dissipated into the air via the housing 3 as well as the heat spreader 4. When the housing 3 is made of a highly thermally conductive material such as a metal or a carbon material, the heat spreader 4 may be omitted from the laminated structure 101.

[0137] As described above, the resin sheet 1 has high thermal conductivity and high heat dissipation in both the surface direction and the thickness direction, and further has high flexibility when heated. Such a heat dissipation structure via the resin sheet 1 in the usage method 1 is something that has never been seen in conventional heat dissipation structures.

[0138] <How to use 2> 3 is a cross-sectional view showing a schematic example of another example of a method of using the resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment) (sometimes referred to as "method of use 2" in this specification). Here, an example is shown in which the resin sheet covers only a part of the exposed surface of the heating element, that is, the heating element is not embedded.

[0139] As shown in FIG. 3(a), the laminated structure 101 prepared in the usage method 2 is the same as the laminated structure 101 prepared in the usage method 1. In the usage method 2, the object to which the resin sheet 1 is applied is the heating element 5, more specifically, the region of the heating element 5 corresponding to a part of the exposed surface 5a, and the height T y is different from that in Usage 1.

[0140] In the second usage method, the heating element 5 is then covered with the resin sheet 1 in the same manner as in the first usage method, as shown in Fig. 3(b). However, at this time, the region of one surface 1a of the resin sheet 1 that is not in contact with the upper surface of the exposed surface 5a of the heating element 5 does not reach a position in the thickness direction of the resin sheet 1 that coincides with the contact portion between the heating element 5 and the connection portion 6, and a part of the lower side (side surface) of the exposed surface 5a of the heating element 5 is left exposed. In this way, the heating element 5 is not embedded in the resin sheet 1.

[0141] Even in this state where the heating element 5 is covered with the resin sheet 1, the flexibility of the resin sheet 1 when heated is high, so that the degree of adhesion between the resin sheet 1 and the heating element 5 is high, as in the case of the usage method 1. More specifically, the occurrence of a gap is suppressed between one surface 1a of the resin sheet 1 and the region of the exposed surface 5a of the heating element 5 that the resin sheet 1 reaches in the thickness direction of the resin sheet 1, and it is also possible to eliminate the existence of the gap (to completely prevent the occurrence of the gap) by adjusting the conditions when the heating element 5 is covered with the resin sheet 1.

[0142] As described above, except for the object to which the resin sheet 1 is applied being different (for example, the resin sheet 1 covers only a portion of the exposed surface 5a of the heating element 5 rather than the entire area), usage method 2 is the same as usage method 1, and the effects achieved by usage method 2 are the same as the effects achieved by usage method 1.

[0143] <Other uses> The method of using the resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment) is not limited to the method of use 1 and the method of use 2, and for example, some of the components in the method of use 1 or the method of use 2 may be changed, deleted, or added.

[0144] For example, when covering the heating element with a resin sheet, the area of ​​one side of the resin sheet (the side facing the circuit board, e.g., one side 1a of the resin sheet 1 in Figures 2 to 3) closest to the circuit board may be positioned in a position in the thickness direction of the resin sheet that coincides with the contact portion between the heating element 5 and the connection portion 6 if it is not in contact with one side of the circuit board (the side facing the resin sheet, e.g., one side 7a of the circuit board 7 in Figures 2 to 3).

[0145] For example, there may be some gaps between one side of the resin sheet (the side facing the circuit board, e.g., one side 1a of the resin sheet 1 in Figures 2 to 3) and the exposed side of the heating element (e.g., exposed surface 5a of the heating element 5 in Figures 2 to 3), and between one side of the resin sheet (the side facing the circuit board, e.g., one side 1a of the resin sheet 1 in Figures 2 to 3) and the connection portion (e.g., connection portion 6 in Figures 2 to 3).

[0146] As described above, the resin sheet of the present embodiment has high flexibility when heated, and therefore has excellent properties for covering and preferably embedding a heat generating element. Therefore, the heat dissipation property of the resin sheet of the present embodiment is extremely excellent. In contrast, conventional heat dissipation sheets such as graphite sheets have excellent heat dissipation properties, but they do not conform to the object to be cooled and have insufficient adhesion to the object to be cooled, making them unsuitable as a heat dissipation structure to be provided alone on a heat generating body.Furthermore, heat dissipation sheets such as graphite sheets are also conductive sheets, and because of their conductivity (because they do not have insulating properties), they cannot be used in the vicinity of an antenna. For example, a thermal interface material (TIM) has adhesion to an object to be cooled and also has insulating properties, but its heat dissipation properties and conformability to an object to be cooled are insufficient. For example, heat dissipation materials that are liquid at room temperature are known, but the use of liquid heat dissipation materials is limited to sealed spaces, and the filling process is complicated and the repairability is poor. The resin sheet of the present embodiment can solve all of these conventional problems. EXAMPLES

[0147] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples. The raw materials and ingredients used in the examples and comparative examples are shown below.

[0148] [Thermoplastic resin] Thermoplastic resin (a1): Ethylene-vinyl acetate copolymer (EVA) (Mitsui Dow Polychemicals "Evaflex (registered trademark) EV150", melting point about 60 °C, MFR 30 g / 10 min, density 0.96 g / cm 3 , vinyl acetate content 33% by mass The MFR of the EVA is a value measured in accordance with JIS K7210:1999 under a temperature condition of 190° C. and a load of 2.16 kg.

[0149] [Plate-shaped filler] Plate-shaped filler (b1): Plate-shaped boron nitride filler (Tokuyama Corporation "K03", average particle size 9 μm, density 2.3 g / cm 3 , thermal conductivity 60W / m K, aspect ratio 30, relative dielectric constant 4) [Connected filler] Connected filler (c1): Magnesium hydroxide filler surface-treated with higher fatty acid ("KISUMA (registered trademark) 5B" manufactured by Kyowa Chemical Industry Co., Ltd., magnesium hydroxide content 95% by mass or more, higher fatty acid content 5% by mass or less, average particle size 0.83 μm, thermal conductivity 8 W / m K) Linked filler (c2): Magnesium hydroxide filler surface-treated with an organosilicon compound (silane coupling agent) ("KISUMA (registered trademark) 5P" manufactured by Kyowa Chemical Industry Co., Ltd., magnesium hydroxide content 95% by mass or more, organosilicon compound content 5% by mass or less, average particle size 0.72 μm, thermal conductivity 8 W / m·K) Linked filler (c3): Magnesium hydroxide filler surface-treated with an organosilicon compound (silane coupling agent) ("KISUMA (registered trademark) 5L" manufactured by Kyowa Chemical Industry Co., Ltd., magnesium hydroxide content 95% by mass or more, organosilicon compound content 5% by mass or less, average particle size 0.72 μm, thermal conductivity 8 W / m·K) Connected filler (c4): Magnesium hydroxide filler (Kyowa Chemical Industry Co., Ltd. "KISUMA (registered trademark) 5", average particle size 0.83 μm, thermal conductivity 8 W / m K) Connected filler (c5): Magnesium hydroxide filler (Kyowa Chemical Industry Co., Ltd. "KISUMA (registered trademark) 8", average particle size 1.38 μm, thermal conductivity 8 W / m K) [Other fillers] Other filler (d1): Card house-shaped aluminum oxide filler (DIC "AC75", average particle size 70 μm, density 3.97 g / cm 3 , thermal conductivity 20W / m K) Other filler (d2): Polyhedral aluminum oxide filler (DIC "AH40-S", average particle size 32 μm, density 3.97 g / cm 3 , thermal conductivity 20W / m K)

[0150] [Example 1] <<Manufacturing of resin sheets>> A pellet-shaped resin composition was prepared by melt-kneading thermoplastic resin (a1) (500 g), plate-like filler (b1) (600 g), linked filler (c1) (250 g), linked filler (c2) (100 g), and linked filler (c3) (100 g) using a twin-screw extruder. Furthermore, the obtained resin composition was sandwiched between a pair of hot plates, heated at 120°C under vacuum conditions of a pressure of 0.02 MPa or less, and molded by vacuum hot pressing at a pressure of 15 MPa for 1 minute to obtain a single-layer resin sheet (thickness 700 μm).

[0151] <<Evaluation of resin sheets>> <Calculation of embedding rate R> The three resin sheets (700 μm thick) obtained by the above method were laminated in the thickness direction and cut into a size of 3.5 cm × 3.5 cm to obtain a laminate with a thickness of T 0 A test piece with a diameter of 2100 μm and a square planar shape was prepared. Next, the obtained test piece was placed on a flat surface, and a cylindrical indenter made of ceramic with a diameter of 16 mm and a height of 14 mm was placed near the center of the exposed surface facing upward of the test piece. At this time, one flat surface of the indenter, not the curved surface, was brought into contact with the exposed surface of the test piece. Furthermore, a weight was placed on the entire surface of the other flat surface (the exposed surface facing upward that is not in contact with the exposed surface of the test piece) of the indenter in this state. In this way, the test piece, the indenter, and the weight were stacked in this order, so that a pressure of 12 kPa was applied to the test piece in its thickness direction. Then, this stack was immediately transferred to an environment of 100°C and left to stand for 10 minutes. As a result, a pressure of 12 kPa was applied to the test piece in the thickness direction of the test piece in an environment of 100°C for 10 minutes. Next, immediately after 10 minutes, the thickness T of the test piece at the part where pressure is being applied in the laminate in this state is measured. 1 The embedment rate R of the test piece (resin sheet) was then calculated using the above formula. The results are shown in Table 1.

[0152] <Confirmation of heat dissipation properties of resin sheet (1)> The resin sheet (thickness: 700 μm) obtained above was cut into a size of 10 cm×10 cm.

[0153] Four resistors were arranged in a row on the circuit surface of the circuit board at approximately equal intervals. The four resistors were given the symbols (1-1) to (1-4) from one end of the row to the other end. Furthermore, in a direction perpendicular to the row direction, a separate resistor was arranged on the same side of the four resistors (i.e., resistor (1-1), resistor (1-2), resistor (1-3), and resistor (1-4)) and approximately equidistant from each of the four resistors. The four separately arranged resistors were given the symbols (2-1) to (2-4) from one end of the row to the other end. The resistor (2-1) is adjacent to the resistor (1-1) and not to the resistor (1-4), the resistor (2-2) is adjacent to the resistor (1-2) and not to the resistor (1-3), the resistor (2-3) is adjacent to the resistor (1-3) and not to the resistor (1-2), and the resistor (2-4) is adjacent to the resistor (1-4) and not to the resistor (1-1). Thus, a total of eight resistors were arranged on the circuit surface of the circuit board, with four resistors per row in two rows, and the intervals between adjacent resistors in two orthogonal directions were approximately equal. The height of these eight resistors (i.e., the distance between the top surface (the surface opposite to the circuit board) of the resistor and the circuit surface of the circuit board) was about 4 mm. A plan view showing the arrangement of the resistors on the circuit board at this time is shown in FIG. 4.

[0154] Next, one thin-wire thermocouple was placed for each of the two resistors at both ends (resistor (1-1) and resistor (1-4)) among the four resistors in one row. Furthermore, one thin-wire thermocouple was placed for the second resistor from one end (resistor (2-2)) among the four resistors in the other row. Then, one thin-wire thermocouple was placed in a portion of the circuit surface of the circuit board that was in the middle of these two rows and also almost the center in the row direction of these two rows (almost the center on the circuit surface of the circuit board), where no resistor was placed. In other words, one thermocouple was placed for each of three of the eight resistors on the circuit surface, and one thermocouple was placed on the circuit surface instead of the resistor. The placement positions of the thermocouples at this time are also shown in Figure 4.

[0155] Next, for all of the eight resistors on the circuit surface, a sheet of thermal interface material (TIM, Widework's "Thermo-TranzH2", 500 μm thick) was laminated for each resistor on the entire surface of the surface opposite the circuit board side. This is to prevent errors in the height of the eight resistors from affecting the evaluation results, since the heights of the eight resistors are not all strictly the same. As a result, the thermocouples on the resistors were placed between the resistors and the thermal interface material (TIM) sheet. Furthermore, the entire surfaces of the thermal interface material sheets opposite the resistor side were collectively covered with the resin sheet (700 μm thick) obtained above. Furthermore, a polycarbonate board (2000 μm thick) was placed on the entire surface of the resin sheet opposite the thermal interface material sheet side after this covering. In this manner, a test circuit board for evaluating the heat dissipation properties of the resin sheet was produced.

[0156] A thermograph was placed on the upper part of the polycarbonate substrate side of the test circuit board obtained above. Next, the voltage was adjusted so that the total power consumption of the eight resistors in the test circuit board was 10 W, and the voltage was applied to the test circuit board. Under these conditions, the temperature of the surface of the polycarbonate board was measured using a thermograph. The image data obtained at this time is shown in Figure 5. Furthermore, the temperatures detected by thermocouples at resistor (1-1), resistor (1-4), resistor (2-2), and the circuit surface are shown in Table 1.

[0157] <Measurement of thermal conductivity in the surface direction of a resin sheet> The thermal conductivity of the resin sheet obtained above was measured in the planar direction using a hot disk method thermal property measuring device (Kyoto Electronics Manufacturing Co., Ltd. "TPS 500 S"). At this time, two resin sheets were sandwiched between insulating materials, and a sensor with a diameter of 7 mm was inserted between these resin sheets to measure the thermal conductivity of the resin sheet. The results are shown in Table 1.

[0158] <Measurement of the relative dielectric constant and dielectric loss tangent of a resin sheet> At room temperature, a test piece of a predetermined size was cut out from the resin sheet obtained above, and the relative dielectric constant at frequencies of 1 GHz and 10 GHz and the dielectric loss tangent at frequencies of 1 GHz and 10 GHz were measured for this test piece in accordance with the TM0m0 mode cavity resonator perturbation method. The results are shown in Table 1.

[0159] <Measurement of density of resin sheet> The density of the resin sheet obtained above was measured in accordance with JIS K 7112: 1999. The results are shown in Table 1.

[0160] <<Production and evaluation of resin sheets>> [Comparative Example 1] A pellet-shaped resin composition was produced by melt-kneading thermoplastic resin (a1) (500 g), another filler (d1) (1000 g), linked filler (c4) (300 g), and linked filler (c5) (300 g) using a twin-screw extruder. A resin sheet (thickness: 700 μm) was produced and evaluated in the same manner as in Example 1, except that this pellet-shaped resin composition was used. The results are shown in Table 1 and Fig. 6. Fig. 6 shows image data acquired when checking the heat dissipation property of the resin sheet in this comparative example.

[0161] [Comparative Example 2] A pellet-shaped resin composition was produced by melt-kneading thermoplastic resin (a1) (500 g), another filler (d2) (1000 g), linked filler (c4) (300 g), and linked filler (c5) (300 g) using a twin-screw extruder. A resin sheet (thickness: 700 μm) was produced and evaluated in the same manner as in Example 1, except that this pellet-shaped resin composition was used. The results are shown in Table 1 and Fig. 7. Fig. 7 shows image data acquired when checking the heat dissipation property of the resin sheet in this comparative example.

[0162] <<Evaluation of test resin sheets>> <Confirmation of heat dissipation properties of test resin sheet> [Test Example 1] A commercially available thermally conductive sheet (thickness 500 μm) whose main component is rubber and whose thermal conductivity in the plane direction is 3 W / m K was prepared as the test resin sheet. In the same manner as in "Confirmation of heat dissipation property of resin sheet" in Example 1, eight resistors and four thermocouples were arranged on the circuit surface of the circuit board. Next, for all of these eight resistors on the circuit surface, a sheet of thermal interface material (TIM, Widework's "Thermo-TranzH2", thickness 500 μm) was laminated for each resistor via the thermocouple when a thermocouple was placed on the entire surface of the surface opposite the circuit board side. As a result, the thermocouple on the resistor was placed between the resistor and the thermal interface material (TIM) sheet. Furthermore, the entire surface of the surface opposite the resistor side of these thermal interface material sheets was collectively covered with the above-mentioned one test resin sheet (thickness 500 μm). Furthermore, one polycarbonate board (thickness 2000 μm) was placed on the entire surface of the surface opposite the thermal interface material sheet side of the covered test resin sheet. In this way, a test circuit board for evaluating the heat dissipation property of the test resin sheet was produced. A voltage was then applied to the test circuit board and the surface temperature of the polycarbonate board was measured using a thermograph in the same manner as in Example 1. The image data obtained at this time is shown in Figure 8. Furthermore, the temperatures detected by the thermocouples on the resistor and circuit surface are shown in Table 1.

[0163] In Table 1, "content (volume %) of flake-like filler" means the ratio of the content (volume parts) of the flake-like filler in the resin sheet to the total volume (volume parts) of the resin sheet. Similarly, the "content (volume %) of connected filler" refers to the ratio of the content (volume parts) of connected filler in the resin sheet to the total volume (volume parts) of the resin sheet. "The ratio (volume %) of the connected filler content to the flake filler content" means the ratio of the connected filler content (volume parts) to the flake filler content (volume parts) in the resin sheet. The same applies to Table 1 and subsequent tables.

[0164] [Table 1]

[0165] As is clear from the above results, in Example 1, the embedding ratio R was high at 43.8%, and the flexibility of the resin sheet when heated was high. As shown in FIG. 5, the surface of the polycarbonate substrate was heated to about 65 to 85°C in the area where the four resistors in the same row were present, spanning these resistors, and this was the same in the area where the two rows were present. Furthermore, the area between these two rows was also heated to about 60 to 65°C. This indicates that the heat generated from the four resistors in the same row was dissipated not only in the length direction of the row but also in the width direction of the row by the resin sheet, and that the resin sheet has high heat dissipation properties in its surface direction. On the other hand, as shown in Table 1, when the temperatures detected by the thermocouples between the same resistors and between the circuit surfaces of the circuit boards in Example 1 and Test Example 1 were compared, the detected temperature in Example 1 was lower than that in Test Example 1. This indicates that the resin sheet of Example 1 has high heat dissipation properties not only in its surface direction but also in its thickness direction, compared to the test resin sheet of Test Example 1 (a commercially available thermally conductive sheet). In the above evaluation, the heat dissipation property of the resin sheet for the heating element (resistor) was simply confirmed without embedding the heating element in the resin sheet, but it was presumed that the resin sheet of Example 1 would exhibit high heat dissipation property even if the heating element was covered over a wider area, preferably by embedding it. Thus, it was confirmed that the resin sheet of Example 1 has high flexibility when heated, high heat dissipation property in both the surface direction and the thickness direction, and is capable of forming a new heat dissipation structure. The resin sheet of Example 1 contained a thermoplastic resin, a flake-like filler, and a connected filler. In the sheet of Example 1, the ratio of the content of the connected filler to the content of the flake-like filler was 72.0% by volume.

[0166] The relative dielectric constant of the resin sheet of Example 1 satisfied the condition of less than 4 at both frequencies of 1 GHz and 10 GHz. The dielectric loss tangent of the resin sheet of Example 1 satisfied the condition of 0.01 or less at both 1 GHz and 10 GHz. The density of the resin sheet of Example 1 is 2 g / cm 3 The following conditions were met.

[0167] In contrast, in Comparative Example 1, the embedding rate R was low at 11.0%, the flexibility of the resin sheet when heated was low, and the resin sheet was unable to cover, or preferably embed, the heating element over a wider area. Furthermore, as shown in FIG. 6, the surface of the polycarbonate substrate was heated to about 65 to 85°C in the area where the four resistors in the same row were present, spanning these resistors, and this was the same in the area where the two rows were present, but the area where such heat was present was narrower than in Example 1. And the area between these two rows was not highly heated. This shows that although the heat generated from the four resistors in the same row was dissipated in the length direction of the row by the resin sheet, the heat dissipation was lower than in Example 1, and furthermore, the heat dissipation in the width direction of the row was also lower than in Example 1, and it showed that the heat dissipation in the surface direction of the resin sheet of Comparative Example 1 was lower than that of the resin sheet of Example 1. On the other hand, as shown in Table 1, when the temperatures detected by the thermocouples of the same resistors were compared between Comparative Example 1 and Test Example 1, the detected temperatures in Comparative Example 1 were all higher than those in Test Example 1, and the resin sheet of Comparative Example 1 had lower heat dissipation than the test resin sheet (commercially available thermally conductive sheet) in Test Example 1. Thus, the resin sheet of Comparative Example 1 had low flexibility when heated and low heat dissipation in both the surface direction and thickness direction. The resin sheet of Comparative Example 1 contained a connecting filler but did not contain a plate-like filler, and instead contained another filler (d1). The other filler (d1) was a card-house shaped aggregate of plate-like aluminum oxide aggregated into spherical shapes.

[0168] In Comparative Example 2, the embedding ratio R was high at 49.5%, and the flexibility of the resin sheet when heated was high. As shown in FIG. 7, the surface of the polycarbonate substrate was heated to about 65 to 85°C in the area where four resistors in the same row were present, spanning these resistors, and this was the same in the area where two rows were present. However, in Comparative Example 2, the area where such heat was present was narrower than in Example 1. And, as in Comparative Example 1, the area between these two rows was not highly heated. These results showed that the resin sheet of Comparative Example 2, like the resin sheet of Comparative Example 1, had lower heat dissipation in its surface direction than the resin sheet of Example 1. On the other hand, as shown in Table 1, when the temperatures detected by thermocouples between the same resistors were compared between Comparative Example 2 and Test Example 1, the detected temperatures were all higher in Comparative Example 2 than in Test Example 1, like Comparative Example 1, and the resin sheet of Comparative Example 2 had lower heat dissipation than the test resin sheet of Test Example 1 (a commercially available thermally conductive sheet). In Comparative Example 2, all of the detected temperatures were higher than those in Comparative Example 1, and the resin sheet in Comparative Example 2 had lower heat dissipation properties than the resin sheet in Comparative Example 1. Thus, the resin sheet in Comparative Example 2 had lower heat dissipation properties in both the surface direction and the thickness direction. The resin sheet of Comparative Example 2 contained a connecting filler but did not contain a plate-like filler, and instead contained another filler (d2). The other filler (d2) was a polyhedral aluminum oxide filler.

[0169] The relative dielectric constants of the resin sheets of Comparative Examples 1 and 2 did not satisfy the condition of 4 or less at either frequency of 1 GHz or 10 GHz. The density of the resin sheets of Comparative Examples 1 and 2 was 2 g / cm 3 The following conditions were not met:

[0170] The test resin sheet of Test Example 1 (a commercially available thermally conductive sheet) did not have flexibility when heated, and was unable to cover or embed the heating element over a wider area. In Test Example 1, as shown in FIG. 8, the surface of the polycarbonate substrate was heated to about 60 to 80°C in the area where four resistors in the same row were present, spanning these resistors, and this was the same in the area where two rows were present. However, in Test Example 1, the area where such heat was present was narrower than in Example 1. And the area between these two rows was not highly heated. These results showed that the resin sheet in Test Example 1 had lower heat dissipation in its surface direction than the resin sheet in Example 1. As described above, when the temperatures detected by thermocouples between the same resistors and between the circuit surfaces of the circuit boards in Test Example 1 and Example 1 were compared, the detected temperatures in Test Example 1 were higher than those in Example 1, and the test resin sheet in Test Example 1 had lower heat dissipation than the resin sheet in Example 1.

[0171] [Example 2] <<Manufacturing of resin sheets>> Except for changing the amount of the pellet-shaped resin composition used, a single-layer resin sheet (thickness: 1500 μm) was produced in the same manner as in Example 1. That is, the resin sheet of this example differed from the resin sheet of Example 1 only in its thickness.

[0172] <<Evaluation of resin sheets>> <Confirmation of heat dissipation properties of resin sheet (2)> The resin sheet (thickness: 1500 μm) obtained above was cut into a size of 10 cm×10 cm.

[0173] As a circuit board equipped with a resistor and a thermocouple, the same one as in Example 1 (shown in FIG. 4) was prepared. Next, the entire surface of the surface opposite the circuit board side of all eight resistors on the circuit surface was covered with the resin sheet (thickness 1500 μm) obtained above, via the thermocouple if one was placed, and pressed. As a result, the thermocouple on the resistor was placed between the resistor and the resin sheet. Furthermore, a polycarbonate board (thickness 2000 μm) was placed on the entire surface of the resin sheet opposite the resistor side after this covering. In this way, a test circuit board for evaluating the heat dissipation property of the resin sheet was produced.

[0174] In this test circuit board, the distance between the resistor side of the polycarbonate substrate and the resistor side of the polycarbonate substrate was measured for each of the eight resistors, and was found to be approximately 400 μm. Therefore, the embedding distance of the resin sheet in the area covering the resistor was approximately 1100 μm (= 1500 μm - 400 μm).

[0175] A thermograph was placed on the upper part of the polycarbonate substrate side of the test circuit board obtained above. Next, the voltage was adjusted so that the total power consumption of the eight resistors in the test circuit board was 10 W, and the voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate board was measured using a thermograph. The temperatures detected by the thermocouples at resistor (1-1), resistor (1-4), resistor (2-2), and the circuit surface are shown in Table 2.

[0176] <<Evaluation of resin sheets>> <Confirmation of heat dissipation properties of resin sheet (2)> [Example 1] The heat dissipation property of the resin sheet of Example 1 (thickness 700 μm) was confirmed by the same method as in Example 2. The temperatures detected by the thermocouple at this time are shown in Table 2.

[0177] In the test circuit board used in this embodiment, the distance between the resistor side of the polycarbonate substrate and the resistor side of the polycarbonate substrate was checked for each of the eight resistors and found to be about 400 μm. Therefore, the embedding distance of the resin sheet in the region covering the resistor was about 300 μm (=700 μm-400 μm). In this example, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) of the polycarbonate substrate was set to the same as in Example 2.

[0178] <<Checking resistor temperature without resin sheet>> [Test Example 2] Except for not using the resin sheet, the test was carried out in the same manner as in Example 2, and the temperature detected by the thermocouple was confirmed. The results are shown in Table 2.

[0179] <<Confirmation of heat dissipation properties of thermal interface material sheet>> [Test Example 3] The heat dissipation properties of the thermal interface material sheet were confirmed in the same manner as in Example 2, except that the same thermal interface material (TIM) sheet as used in Test Example 1 was used instead of the resin sheet (thickness 1500 μm). In this test example, the entire surface of the surface opposite to the circuit board side of all eight resistors on the circuit surface was collectively covered with one thermal interface material sheet via a thermocouple when a thermocouple was placed. In this test example, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) surface of the polycarbonate board was the same as in Example 2. The temperature detected by the thermocouple at this time is shown in Table 2. In this test example, the thermocouple on the resistor was placed between the resistor and the thermal interface material. The results are shown in Table 2.

[0180] [Table 2]

[0181] As is clear from the above results, when the temperatures detected by thermocouples between the same resistors and between the circuit surfaces of the circuit boards in Examples 1 and 2 and Test Example 2 were compared, the detected temperatures in Examples 1 and 2 were significantly lower than that in Test Example 2. This was because Test Example 2 did not have a heat dissipation structure. Furthermore, when the temperatures detected by the thermocouples between the same resistors and between the same circuit surfaces of the circuit boards in Examples 1 and 2 and Test Example 3 were compared, the detected temperatures in Examples 1 and 2 were lower than that in Test Example 3. This indicates that the resin sheets of Examples 1 and 2 have higher heat dissipation properties not only in the surface direction but also in the thickness direction than the thermal interface material sheet of Test Example 3. The thermal interface material sheet of Test Example 3 had inferior embeddability to the resin sheets of Examples 1 and 2. Although the above evaluation also confirmed the heat dissipation of the resin sheet from the heating element (resistor) in a simple manner without embedding the heating element in the resin sheet, it was presumed that the resin sheet of Example 2 would exhibit high heat dissipation properties by covering the heating element over a wider area, preferably by embedding it, as with the resin sheet of Example 1. In this way, it was confirmed that the resin sheet of Example 2 has high flexibility when heated, high heat dissipation properties in both the surface direction and the thickness direction, and is capable of forming a new heat dissipation structure.

[0182] Furthermore, when the temperatures detected by the thermocouples between the same resistors and between the circuit surfaces of the circuit boards in Example 1 and Example 2 were compared, the detected temperature in Example 2 was lower than that in Example 1. This was because the embedding distance of the resin sheet in Example 2 was longer than that in Example 1, and therefore the heat dissipation effect of the resin sheet was higher.

[0183] [Example 3] <<Manufacturing of resin sheets>> A single-layer resin sheet (thickness 1500 μm) was produced in the same manner as in Example 1, except that the contents of the components contained in the resin sheet were changed as shown in Table 3 and the amount of the pellet-shaped resin composition used was changed.

[0184] <<Evaluation of resin sheets>> <Calculation of embedding rate R> For the resin sheet obtained above, the embedment ratio R was calculated in the same manner as in Example 1. The results are shown in Table 3.

[0185] <Confirmation of heat dissipation properties of resin sheet (3)> The resin sheet (thickness: 1500 μm) obtained above was cut into a size of 5 cm×5 cm.

[0186] One resistor was placed on the circuit surface of the circuit board. The height of the resistor (i.e., the distance between the upper surface of the resistor (the surface opposite to the circuit board) and the circuit surface of the circuit board) was 1.2 mm. Next, a thin-wire thermocouple was placed on the resistor. Furthermore, one thin-wire thermocouple was placed on the surface (back surface) opposite the circuit surface of the circuit board, in a position directly below the resistor.

[0187] Next, the entire surface of the resistor on the circuit surface opposite the circuit board side was covered with one resin sheet (thickness 1500 μm) obtained above via a thermocouple and pressed. As a result, the thermocouple on the resistor was disposed between the resistor and the resin sheet. Furthermore, one polycarbonate substrate (thickness 2000 μm) was placed on the entire surface of the resin sheet after covering opposite the resistor side. In this way, a test circuit board for evaluating the heat dissipation property of the resin sheet was produced.

[0188] In this test circuit board, the distance between the resistor side of the polycarbonate board and the resistor side of the polycarbonate board was approximately 400 μm. In this test circuit board, the area of ​​the resin sheet side facing the circuit board that was not in contact with the resistor was in contact with the circuit board (more specifically, the circuit surface), and the resistor was completely embedded in the resin sheet.

[0189] A thermograph was placed on the upper part of the polycarbonate substrate side of the test circuit board obtained above. Next, the voltage was adjusted so that the power consumption of the resistor in the test circuit board was 2.5 W, and the voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate board was measured using a thermograph. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0190] <Measurement of thermal conductivity, dielectric constant, dielectric tangent and density in the surface direction of a resin sheet> For the resin sheet obtained above, the thermal conductivity, relative dielectric constant, dielectric loss tangent, and density were measured in the same manner as in Example 1. The results are shown in Table 3.

[0191] [Example 4] <<Manufacturing of resin sheets>> A single-layer resin sheet (thickness 1500 μm) was produced in the same manner as in Example 1, except that the contents of the components contained in the resin sheet were changed as shown in Table 3 and the amount of the pellet-shaped resin composition used was changed.

[0192] <<Evaluation of resin sheets>> <Calculation of embedding rate R> For the resin sheet obtained above, the embedment ratio R was calculated in the same manner as in Example 1. The results are shown in Table 3.

[0193] <Confirmation of heat dissipation properties of resin sheet (3)> The heat dissipation property of the resin sheet obtained above was confirmed by the same method as in Example 3. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0194] In the test circuit board used in this example, the distance between the resistor side surface of the polycarbonate board and the resistor side surface of the polycarbonate board was confirmed to be about 400 μm. In this test circuit board, as in Example 3, the area of ​​the circuit board side surface of the resin sheet that was not in contact with the resistor was in contact with the circuit board (more specifically, the circuit surface), and the resistor was completely embedded in the resin sheet.

[0195] <Measurement of thermal conductivity, dielectric constant, dielectric tangent and density in the surface direction of a resin sheet> For the resin sheet obtained above, the thermal conductivity, relative dielectric constant, dielectric loss tangent, and density were measured in the same manner as in Example 1. The results are shown in Table 3.

[0196] <<Checking resistor temperature without resin sheet>> [Test Example 4] Except for not using the resin sheet, the test was carried out in the same manner as in Example 3, and the temperature detected by the thermocouple was confirmed. The results are shown in Table 3.

[0197] <<Confirmation of heat dissipation properties of thermal interface material sheet>> [Test Example 5] As a circuit board equipped with a resistor and a thermocouple, the same one as in Example 3 was prepared. Next, the entire surface of the resistor on the circuit surface opposite to the circuit board side was covered with one thermal interface material (TIM) sheet, the same as that used in Test Example 1, via a thermocouple, and pressed. That is, in this test example, unlike the cases of Examples 3 and 4, a thermal interface material sheet was used instead of a resin sheet (thickness 1500 μm). As a result, the thermocouple on the resistor was placed between the resistor and the thermal interface material sheet. Furthermore, a polycarbonate substrate (thickness 2000 μm) was placed on the entire surface of the thermal interface material sheet opposite to the resistor side after this covering. In this manner, a test circuit board for evaluating the heat dissipation property of the thermal interface material sheet was produced. In this test example, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) of the polycarbonate substrate was set to the same as in Example 3.

[0198] A thermograph was placed on the upper part of the polycarbonate substrate side of the test circuit board obtained above. Next, the voltage was adjusted so that the power consumption of the resistor in the test circuit board was 2.5 W, and the voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate board was measured using a thermograph. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0199] [Table 3]

[0200] As is clear from the above results, when comparing the temperatures detected by thermocouples between resistors and between the rear surfaces of the circuit boards in Examples 3 and 4 and Test Example 4, the detected temperatures in Examples 3 and 4 were significantly lower than that in Test Example 4. This was because Test Example 4 did not have a heat dissipation structure. Furthermore, when the temperatures detected by the thermocouples between the resistors and between the back surfaces of the circuit boards in Examples 3 to 4 and Test Example 5 were compared, the detected temperatures in Examples 3 to 4 were lower than that in Test Example 5. This indicates that the resin sheets of Examples 3 to 4 have higher heat dissipation properties not only in the surface direction but also in the thickness direction than the thermal interface material sheet of Test Example 5. The thermal interface material sheet of Test Example 5 had inferior embeddability to the resin sheets of Examples 3 to 4. In this way, it was confirmed that the resin sheets of Examples 3 and 4 have high flexibility when heated, high heat dissipation properties in both the surface direction and the thickness direction, and can form a new heat dissipation structure.

[0201] Furthermore, when comparing the temperatures detected by thermocouples between resistors and between the back surfaces of the circuit boards in Example 3 and Example 4, the detected temperature in Example 4 was lower than that in Example 3. This was based on the difference in the composition of the resin sheet, and was because the heat dissipation effect of the resin sheet in Example 4 was higher than that in Example 3, and was consistent with the results of the thermal conductivity in the surface direction of these resin sheets.

[0202] The resin sheets of Examples 3 and 4 contained a thermoplastic resin, a flake-like filler, and a connected filler. In the sheets of Examples 3 and 4, the ratio of the content of the connected filler to the content of the flake-like filler was 99.1 to 296.6% by volume.

[0203] The resin sheet of Example 3 met the UL94 standard grade V-2 (1.5 mmt), and the resin sheet of Example 4 met the UL94 standard grade V-0 (1.5 mmt).

[0204] The relative dielectric constant of the resin sheets of Examples 3 and 4 satisfied the condition of 4 or less at both frequencies of 1 GHz and 10 GHz. The dielectric loss tangents of the resin sheets of Examples 3 and 4 satisfied the condition of less than 0.01 at both 1 GHz and 10 GHz. The density of the resin sheets in Examples 3 and 4 was 2 g / cm 3 The following conditions were met. [Industrial Applicability]

[0205] The present invention can be used to configure a new heat dissipation structure in electronic devices equipped with a CPU, and is not limited to CPUs, but can also be used to configure a heat dissipation structure in other devices equipped with the same heat generating element as a CPU. [Explanation of symbols]

[0206] 1...Resin sheet 3. Housing 4. Heat spreader 5. Heating element 6 Connection 7. Circuit board 8... weight 9. Pressed material 10. Test piece D S ...Plane direction of resin sheet D T ...Thickness direction of resin sheet T 0 ...Thickness of test piece T 1 ...Thickness of the test piece at the pressurized area after heating and pressing

Claims

1. A resin sheet, The resin sheet includes a thermoplastic resin, a plate-like filler, and a connecting filler, The average particle size of the connected filler is 2 μm or less, The resin sheet has a dielectric loss tangent of 0.01 or less at a frequency of 10 GHz, measured in accordance with a TM0m0 mode cavity resonator perturbation method.

2. A resin sheet, The resin sheet includes a thermoplastic resin, a plate-like filler, and a connecting filler, The average particle size of the connected filler is 2 μm or less, A test piece having a thickness of T0, which is one of the resin sheets or a laminate of two or more of the resin sheets, is used, and a pressure of 12 kPa is applied to the test piece in the thickness direction of the test piece for 10 minutes in an environment of 100°C. When the thickness T1 of the test piece at the part where the pressure is applied is measured, the thickness T1 of the test piece is calculated by the following formula: R=(T ０ -T １ ) / T ０ ×100 The embedding rate R calculated by is 30% or more, The resin sheet has a dielectric loss tangent of 0.01 or less at a frequency of 10 GHz, measured in accordance with a TM0m0 mode cavity resonator perturbation method.

3. The resin sheet according to claim 1, wherein the resin sheet has a relative dielectric constant of 4 or less at a frequency of 10 GHz measured in accordance with a TM0m0 mode cavity resonator perturbation method.

4. The resin sheet according to claim 1 or 3, wherein the flake-like filler is made of boron nitride or aluminum oxide.

5. The resin sheet according to claim 1 or 3, wherein the connecting filler comprises magnesium hydroxide.

6. The resin sheet according to claim 1 or 3, wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer.

7. 4. The resin sheet according to claim 1, wherein the ratio of the content of the connecting filler to the content of the plate-like filler in the resin sheet is 60 to 140% by volume.

8. The resin sheet according to claim 1 or 3, wherein the average particle diameter of the flake-like filler is 5 μm or more and 15 μm or less.

9. The resin sheet according to claim 1 or 3, wherein the density of the resin sheet is 1 to 2 g / cm 3 .

10. The resin sheet according to claim 2, wherein the resin sheet has a relative dielectric constant of 4 or less at a frequency of 10 GHz measured in accordance with a TM0m0 mode cavity resonator perturbation method.

11. The resin sheet according to claim 2 or 10, wherein the flake-like filler is made of boron nitride or aluminum oxide.

12. The resin sheet according to claim 2 or 10, wherein the connecting filler comprises magnesium hydroxide.

13. The resin sheet according to claim 2 or 10, wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer.

14. The resin sheet according to claim 2 or 10, wherein the ratio of the content of the connecting filler to the content of the plate-like filler in the resin sheet is 60 to 140% by volume.

15. The resin sheet according to claim 2 or 10, wherein the average particle diameter of the flake-like filler is 5 μm or more and 15 μm or less.

16. The resin sheet according to claim 2 or 10, wherein the density of the resin sheet is 1 to 2 g / cm 3 .

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