Resin sheet

Abstract

Provided is a novel resin sheet (1) capable of constituting a novel heat dissipation structure having a high heat dissipation effect, the resin sheet (1) including a thermoplastic resin, a plate-shaped filler, and a connection filler, wherein the average particle diameter of the connection filler is 2 μm or less. When a test piece (10) which is a single sheet of the resin sheet (1) or a laminate of two or more sheets of the resin sheet (1) and has a thickness of T0 is used, a pressure of 12 kPa is applied to the test piece (10) in the thickness direction of the test piece (10) for 10 minutes in an environment of 100°C, and a thickness T1 of the test piece (10) at a site where the pressure is applied is measured, an embedding rate R calculated by R = (T0 - T1) / T0 × 100 may be 30% or more.

Description

Resin sheet

[0001] The present invention relates to a resin sheet. This application claims priority based on Japanese Patent Application No. 2023-98720 filed in Japan on June 15, 2023, and Japanese Patent Application No. 2023-148498 filed in Japan on September 13, 2023, the contents of which are incorporated herein by reference.

[0002] A central processing unit (abbreviated as "CPU" in this specification) is one of the typical devices that make up a computer. The amount of heat generated by a CPU increases dramatically when the computer is running. 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. As a result, measures to reduce heat generated by electronic devices have become extremely important.

[0003] In typical electronic devices, 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. As a result, 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 surface direction by the plate-shaped 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 for adopting such a heat dissipation structure for a CPU in the past is as follows: A heat spreader is made of metal, graphite, or the like, and has high thermal conductivity in its surface direction and high heat dissipation properties, but it does not conform to the object to be cooled (the CPU), has insufficient adhesion to the object to be cooled (the CPU), and is not insulating. On the other hand, a TIM has a certain degree of conformability to the object to be cooled (the CPU), good adhesion, and is insulating, but has insufficient thermal conductivity. Therefore, by using a combination of these (a heat spreader and a TIM) and adopting the above-mentioned heat dissipation structure, these drawbacks are compensated for.

[0005] International Publication No. 2018 / 139364

[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. Furthermore, as a replacement for the TIM, considering the need for insulation and conformability, a resin sheet would be appropriate, but no resin sheet with a high heat dissipation effect has been known to date. While the above explanation has been given using a CPU as an example, similar problems can occur in other devices that have a heat generating element similar to a CPU.

[0007] An object of the present invention is to provide a novel resin sheet that can form a new heat dissipation structure with a high heat dissipation effect.

[0008] The present invention employs the following configurations: [1] A resin sheet comprising a thermoplastic resin, a plate-like filler, and a connecting filler, wherein the connecting filler has 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, wherein the connecting filler has an average particle size of 2 μm or less, and wherein the resin sheet is one of the resin sheets or a laminate of two or more of the resin sheets, and wherein the thickness is T ０ A test piece of this example was used, and a pressure of 12 kPa was applied to the test piece in the thickness direction of the test piece 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 of the resin sheet is 30% or more.

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

[0010] [5] The resin sheet according to [1], [3], or [4], wherein the flake 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 connecting filler to the content of the flake filler is 60 to 140 volume %. [9] The resin sheet according to any one of [1] and [3] to [8], wherein the average particle size of the flake filler is 5 μm or more.

[0011]

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

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

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

[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 average particle diameter of the flake filler is 5 μm or more.

[0012] According to the present invention, a novel resin sheet is provided that can constitute a new heat dissipation structure with a high heat dissipation effect.

[0013] 2A and 2B are cross-sectional views for schematically explaining a method for calculating the embedment rate R of a test piece using a resin sheet according to one embodiment of the present invention, showing a cross-sectional view of a laminate in which a test piece, an indentation material, and a weight are stacked before heating and pressurizing. FIG. 2B is a cross-sectional view for schematically explaining a method for calculating the embedment rate R of a test piece using a resin sheet according to one embodiment of the present invention, showing a cross-sectional view of a laminate in which a test piece, an indentation material, and a weight are stacked immediately after heating and pressurizing. FIG. 2C is a cross-sectional view schematically showing an example of a method for using a resin sheet according to one embodiment of the present invention, showing a state before a heating element is covered with a resin sheet. FIG. 2D is a cross-sectional view showing a state in which the resin sheet and / or heating element 5 shown in FIG. 2A is moved, and the entire area of ​​the heating element and connection parts is covered with the resin sheet. FIG. 2E is a cross-sectional view schematically showing another example of a method for using a resin sheet according to one embodiment of the present invention, showing a state before the heating element is covered with a resin sheet. FIG. 3A is a cross-sectional view showing a state in which the resin sheet and / or heating element shown in FIG. 3A is moved, and a portion of the heating element is covered with the resin sheet. FIG. 1 is a plan view schematically showing the positions of resistors and thermocouples on a circuit board when the heat dissipation ability of a resin sheet or a test resin sheet from a heating element is confirmed in Examples 1 and 2, Comparative Examples 1 and 2, and Test Examples 1 to 3. FIG. 2 is image data showing the confirmation results of the heat dissipation ability of a resin sheet from a heating element in Example 1. FIG. 3 is image data showing the confirmation results of the heat dissipation ability of a resin sheet from a heating element in Comparative Example 1. FIG. 4 is image data showing the confirmation results of the heat dissipation ability of a resin sheet from a heating element in Comparative Example 2. FIG. 5 is image data showing the confirmation results of the heat dissipation ability of a test resin sheet from a heating element in Test Example 1.

[0014] <<Resin Sheet (First Aspect)>> A 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, wherein the connecting filler has an average particle size of 2 μm or less, and is one of the resin sheets or a laminate of two or more of the resin sheets, and has a thickness of T ０ A test piece of this example was used, and a pressure of 12 kPa was applied to the test piece in the thickness direction of the test piece 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 -T１ ) / T ０ × 100, the embedding ratio R is 30% or more. Because the resin sheet of the first embodiment contains the plate-like filler and the linked filler, it has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and its thickness direction. Furthermore, the resin sheet of the first embodiment contains a thermoplastic resin, and its embedding ratio R is 30% or more, resulting in high flexibility when heated. By covering, or preferably embedding, a heat-generating element such as a central processing unit (CPU) with the resin sheet of the first embodiment having such properties, a new heat dissipation structure can be configured in various electronic devices, resulting in a high heat-generating effect in various electronic devices. Furthermore, this heat dissipation structure can be configured not only for CPUs but also for other devices equipped with a heat-generating element similar to a CPU, resulting in a high heat-generating effect. In this specification, the "direction parallel to the surface" may be referred to as the "surface direction," not limited to the case of a resin sheet.

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

[0016] <Thermoplastic Resin> The resin sheet contains the thermoplastic resin, and thus can maintain a sheet shape and has conformability and adhesiveness 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 embedding ratio R.

[0018] The resin sheet can be produced, for example, by molding (pressure-heat molding) a resin composition described below for producing the resin sheet. In this case, the thermoplastic resin preferably has a melting point lower than the heating temperature (molding temperature) during molding of the resin composition. 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 lower, and may be, for example, either 80°C or lower or 70°C or lower. By using a thermoplastic resin with a melting point equal to or lower 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 with a melting point of 35°C or higher can be more easily obtained or produced. In one embodiment, the melting point of the thermoplastic resin may be, for example, any of 35 to 90°C, 35 to 80°C, and 35 to 70°C. However, these are only examples of the melting points of thermoplastic resins.

[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, 5 to 40 g / 10 min or 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 higher conformability 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. 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 K7210:1999.

[0021] Preferred examples of the thermoplastic resin include ethylene-vinyl acetate copolymer (EVA). Ethylene-vinyl acetate copolymers have a lower melting point than other resins and exhibit endothermic properties at or near their melting point when heated. Therefore, resin sheets containing ethylene-vinyl acetate copolymers have higher heat dissipation properties due to their heat-storing latent heat function. Furthermore, ethylene-vinyl acetate copolymers have flexibility, impact resistance, and adhesiveness, so that when a heating element is covered with a resin sheet containing ethylene-vinyl acetate copolymer, the resin sheet easily adheres to the heating element. Furthermore, because ethylene-vinyl acetate copolymers are polar, they can be composited with flame retardants (e.g., magnesium hydroxide), making it easy to impart flame retardancy to the resin sheet.

[0022] In the ethylene-vinyl acetate copolymer, the ratio of the amount (parts by mass) of structural units derived from vinyl acetate to the total amount (parts by mass) of structural units (sometimes referred to herein as the "vinyl acetate content") is preferably 10 to 40% by mass, and may be, for example, 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 conformability and adhesion of the resin sheet to the object to which it is applied are improved. 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, workability during production of the resin sheet is improved.

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

[0024] The thermoplastic resin contained in the resin sheet is preferably an ethylene-vinyl acetate copolymer, since this allows the effects of the present invention to be more pronounced.

[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 the thermoplastic resin in the resin sheet] / [total mass (parts by mass) of the 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 greater than the lower limit, the effect obtained by the resin sheet containing the thermoplastic resin is enhanced. 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 is preferably 45% by mass or less, more preferably 40% by mass or less. When the ratio is equal to or less than the upper limit, the effect obtained by 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% by mass, 25 to 45% by mass, and 30 to 45% by mass, or any one of 20 to 40% by mass, 25 to 40% by mass, and 30 to 40% by mass. However, these are just examples of the ratios, and the ratios are 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 a 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 cold nor hot, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0027] <Flat-Like Filler> The resin sheet contains the plate-like filler, which improves its heat dissipation properties. In a resin sheet, the plate-like filler tends 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. This increases the thermal conductivity of the resin sheet in the surface direction, thereby improving the heat dissipation properties in the surface direction. For example, if a filler other than a plate-like filler, such as a polyhedral filler or a card-house-shaped filler (a filler in which plate-like fillers aggregate to form secondary particles), is used instead of the plate-like filler, the heat dissipation properties of the resin sheet in the surface direction will be reduced. Furthermore, the card-house-shaped 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, either 10 to 30 or 30 to 50. When the aspect ratio of the plate-like filler is in such a range, the effect obtained by the resin sheet containing the plate-like filler is further enhanced.

[0029] The particle diameter of the plate-like filler can be, for example, the maximum length of a line segment connecting two different points on the periphery of the plate-like filler. The thickness of the plate-like filler can be, for example, the maximum distance between the main surfaces of the plate-like filler. The aspect ratio of the plate-like filler can be, for example, the average aspect ratio of 50 randomly selected plate-like fillers.

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

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

[0032] The thermal conductivity of the plate-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 plate-like filler is not particularly limited. For example, plate-like fillers with a thermal conductivity of 400 W / m·K or less are more easily available. In one embodiment, the thermal conductivity of the plate-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 only examples of the thermal conductivities of the plate-like fillers.

[0033] The thermal conductivity of fillers, including plate-like fillers, 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 reduce the dielectric constant of the resin sheet described below, the dielectric constant of the flake-like filler is preferably 5.5 or less, more preferably 4.5 or less. On the other hand, the lower limit of the dielectric constant of the flake-like filler is not particularly limited. For example, a flake-like filler having a 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 filler or two or more types of fillers. When two or more types of fillers are used, the combination and ratio thereof can be selected arbitrarily 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 not only has high heat dissipation properties, but also has better fluidity when heated and has better conformability to an object to which the resin sheet is applied, so that, 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] The plate-like filler is more preferably 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 furthermore, since its relative dielectric constant is further reduced, it has further preferable properties as described below.

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

[0040] <Connecting Filler> The resin sheet contains the connecting filler, which improves its heat dissipation properties. The connecting filler in the resin sheet is widely distributed in both the surface direction and thickness direction of the resin sheet, and as described below, the size of the connecting filler is small. Therefore, the connecting filler maintains contact with the plate-like fillers in both the surface direction and thickness direction of the resin sheet, thereby connecting the plate-like fillers to each other through itself. As a result, the thermal conductivity and heat dissipation properties are increased in both the surface direction and thickness direction of the resin sheet. In particular, the resin sheet contains the connecting filler, which improves its thermal conductivity in the thickness direction and improves its heat dissipation properties. If the resin sheet does not contain the connecting filler, the heat dissipation properties in the thickness direction of the resin sheet would not be as high.

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

[0042] The shape of the connected filler is not particularly limited, but is preferably a shape having a flat surface, and more preferably a plate-like shape. Having a flat surface, particularly a plate-like shape, of the connected filler increases the contact area between the connected filler and the plate-like filler. As described above, the plane direction of the plate-like filler tends to be oriented in the same direction as the plane direction of the resin sheet or in a direction close to the plane direction of the resin sheet. Therefore, even if the connected filler has a flat surface, the more the overall shape of the connected filler deviates from a plate shape, the smaller the contact area between the connected filler and the plate-like filler tends to be. However, by having the average particle diameter of the connected filler be 2 μm or less, sufficient contact between the connected 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 improved the fluidity of the resin sheet when heated, and the higher the ability of the resin sheet to conform to the object to which it is applied. For example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet.

[0044] The thermal conductivity of the connected 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 connected filler is not particularly limited. For example, connected fillers with a thermal conductivity of 400 W / m·K or less are more easily available. In one embodiment, the thermal conductivity of the connected 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 examples of the thermal conductivities of the connected filler.

[0045] Examples of materials for 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. The use of a surface-treated linked filler improves the affinity between the linked filler and a resin such as a thermoplastic resin, improving the fluidity of the resin sheet and thereby enhancing the conformability and adhesion of the resin sheet to the object to which it is applied. Examples of surface treatments for the linked 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 two or more types of connecting fillers. When two or more types of connecting fillers are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0048] The connecting filler is magnesium hydroxide (Mg(OH) ２ 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 content of the connected filler to the content of the plate-like filler ([content of connected filler in resin sheet (volume parts)] / [content of plate-like filler in resin sheet (volume parts)] × 100) is preferably 60% by volume or more, and may be, for example, any one of 65% by volume or more, 70% by volume or more, 90% by volume or more, and 200% by volume or more. When the ratio is equal to or greater 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, is further enhanced. In one embodiment, the ratio is preferably 60 to 300% by volume, and may be, for example, any one of 65 to 300% by volume, 70 to 300% by volume, 90 to 300% by volume, and 200 to 300% by volume, any one of 60 to 250% by volume, 65 to 250% by volume, 70 to 250% by volume, and 90 to 250% by volume, any one of 60 to 140% by volume, 65 to 140% by volume, 70 to 140% by volume, and 90 to 140% by volume, any one of 60 to 110% by volume, 65 to 110% by volume, 70 to 110% by volume, and 90 to 110% by volume, or any one of 60 to 80% by volume, 65 to 80% by volume, and 70 to 80% by volume. However, these are just examples of the ratios.

[0051] In the resin sheet, the ratio of the content (volume parts) of the connected filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of the connected filler in the resin sheet] / [total volume (volume parts) of the resin sheet] × 100) is preferably within 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 is, for example, preferably 6% by volume or more, and may be, for example, any one of 9.8% by volume or more, 14% by volume or more, 20% by volume or more, and 25% by volume or more. When the ratio is equal to or greater than the lower limit, the effects obtained by using the connected filler are further enhanced. In the resin sheet, the ratio of the content (volume parts) of the connected filler to the total volume (volume parts) of the resin sheet is preferably 49% by volume or less, and may be, for example, any one of 33% by volume or less and 21% by volume or less. When the ratio is equal to or less than the upper limit, the effects obtained by using a filler other than the connected filler, such as the plate-like filler, are further enhanced. 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%, or any one of 6 to 21 volume%, 9.8 to 21 volume%, and 14 to 21 volume%, although these are just examples of the ratio.

[0052] <Other Components> 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, within a range that does not impair the effects of the present invention. 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 two or more types are contained, the combination and ratio thereof can be selected arbitrarily depending on the purpose.

[0054] Examples of the other components include additives known in the art, such as 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% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or greater than the lower limit, the heat dissipation properties and flexibility when heated of the resin sheet are well balanced and improved. On the other hand, the ratio is 100% by mass or less. The ratio is usually the same as the ratio of the total content (parts by mass) of the thermoplastic resin, the platy filler, and the linked 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 platy filler in resin composition] + [content (parts by mass) of linked filler in resin composition]) / [total content (parts by mass) of components that do not vaporize at room temperature in the 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 equal to or greater than the lower limit, the heat dissipation properties of the resin sheet are improved. On the other hand, the thickness of the resin sheet is preferably 2000 μm or less, and may be, for example, any one of 1500 μm or less and 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 improved. In one embodiment, the thickness of the resin sheet may be, for example, any one of 100 to 2000 μm, 300 to 1500 μm, 500 to 1000 μm, and 800 to 1500 μm. However, these are examples of the thickness of the resin sheet. As described below, the thickness of the resin sheet is preferably adjusted depending on the thickness of the object to which the resin sheet is to be applied.

[0057] <Characteristics of Resin Sheet> [Embedding R] When there is one resin sheet and its thickness is T ０ or a laminate of two or more of the resin sheets, and the thickness thereof is T ０ A test piece of the above 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, and the thickness T of the test piece at the part where the pressure is applied is measured. １ When the measurement was performed, the following formula: R = (T ０ -T １ ) / T ０ The embedding ratio R calculated by multiplying the embedding ratio R by 100 is 30% or more. The resin sheet of the first embodiment, in which the embedding ratio R is in this range, has high flexibility when heated. Therefore, the heat generating element can be well covered by the resin sheet. The method for calculating the embedding ratio R will be described in more detail below with reference to the drawings.

[0058] 1A and 1B are cross-sectional views for schematically explaining a method for calculating the embedment ratio R of the test piece using the resin sheet. Note that the drawings used in the following explanation may show enlarged essential 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 pressurization, as shown in FIG. 1A, the test piece 10 is placed on a flat surface, and an indenter 9 is placed near the center of one surface 10a, which is the upward exposed surface of the test piece 10. The indenter 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 itself or a laminate of two or more of the resin sheets. Regardless of which type of test piece 10 is used, the thickness of the test piece 10 in the thickness direction 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, or any of 3500 μm or less, 3000 μm or less, and 2500 μm or less.

[0060] 1A and 1B, the contents of the test piece 10 (resin sheet) are not shown. Also in Fig. 2A and 2B and subsequent figures, the contents of the resin sheet are not shown in the cross-sectional views of the resin sheet of this embodiment.

[0061] The constituent material of the indenter 9 is not particularly limited as long as it is hard, and examples thereof include various ceramics. The shape of the indenter 9 is not particularly limited as long as the contact portion with the test piece 10 is flat, and may be, for example, a prism, a truncated pyramid, a cylinder, a truncated cone, an elliptical cylinder, an elliptical truncated ...

[0062] Next, a weight 8 is placed on the other surface 9a of the indentation material 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 indentation material 9, or on the entire surface. The weights 8 placed on the indentation material 9 may be one or two or more. In this way, by placing the weight 8 on the indentation material 9 and stacking the test piece 10, indentation material 9, and weight 8 in this order to form a 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 a result, a pressure of 12 kPa is applied to the test piece 10 in the thickness direction of the test piece 10 for 10 minutes in an environment at 100°C. When the laminate 100 is placed in an environment at 100°C, the heated test piece 10 softens and is pressed by the indenter 9, causing the contact portion of the test piece 10 with the indenter 9 to dent. Next, immediately after 10 minutes have passed, the thickness T of the test piece 10 at the pressure-applied portion of the laminate 100 in this heated and pressurized state is measured. １ Measure.

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

[0065] In order to allow the heat generating element to be easily covered by the resin sheet, the embedding ratio R is preferably 35% or more, and may be, for example, 40% or more, 45% or more, or 50% or more. On the other hand, the upper limit of the embedding ratio R is not particularly limited. For example, a resin sheet having an embedding ratio R of 65% or less or 60% or less can be more easily manufactured. In one embodiment, the embedding ratio R may be, for example, any of 30 to 65%, 35 to 65%, 40 to 65%, 45% to 65%, and 50 to 65%, or any of 30 to 60%, 35 to 60%, 40 to 60%, and 45 to 60%. However, these are just examples of the embedding ratio R.

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

[0067] [Thermal Conductivity in the Planar Direction] The thermal conductivity of the resin sheet in the planar 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. A resin sheet having a thermal conductivity equal to or greater than the lower limit has high heat dissipation properties in its planar direction. The upper limit of the thermal conductivity of the resin sheet in the planar direction 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, 2 to 15 W / m·K, 3 to 15 W / m·K, or 4 to 15 W / m·K. The thermal conductivity of a resin sheet in the planar direction, not limited to the resin sheet, more specifically refers to the thermal conductivity of the resin sheet in a direction parallel to one or the other of the surfaces of the resin sheet.

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

[0069] The thermal conductivity in the plane 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 plate-like filler and its content in the resin sheet; the type of connecting filler and its content in the resin sheet; the thickness of the resin sheet, etc.

[0070] [Dielectric Constant] The 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, 3.75 or less, 3.65 or less, or 3.55 or less. Resin sheets having a dielectric constant at a frequency of 10 GHz or less below the upper limit have high insulating properties and are particularly suitable for covering and attaching a heating element on a circuit board, for example, because they are highly effective in suppressing the generation of noise in electrical signals in circuits within the object to which the resin sheet is attached. The lower limit of the dielectric constant at a frequency of 10 GHz is not particularly limited. For example, resin sheets having a dielectric constant of 1 or more at a frequency of 10 GHz can be more easily manufactured. In one embodiment, the dielectric constant at a frequency of 10 GHz may be, for example, 1 to 4, 1 to 3.75, 1 to 3.65, or 1 to 3.55. However, these are examples of the 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 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, 3.9 or less or 3.8 or less. Resin sheets having a dielectric constant at a frequency of 1 GHz or less have high insulating properties and are particularly suitable for covering and attaching a heating element on a circuit board, for example, because they are highly effective in suppressing the generation of noise in electrical signals in circuits within an object to which the resin sheet is attached. The lower limit of the dielectric constant at a frequency of 1 GHz is not particularly limited. For example, resin sheets having a dielectric constant of 1 or more at a frequency of 1 GHz can be more easily manufactured. In one embodiment, the dielectric constant at a frequency of 1 GHz may be, for example, 1 to 4, 1 to 3.9, or 1 to 3.8. However, these are examples of the dielectric constant at a frequency of 1 GHz. The dielectric constant at a frequency of 1 GHz is preferably measured at room temperature (e.g., 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] [Dielectric Loss Tangent] 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, 0.0065 or less, 0.0055 or less, or 0.0045 or less. Resin sheets having a dielectric loss tangent at a frequency of 10 GHz in this range have high radio wave transmittance and are suitable for constructing electronic devices equipped with antennas. The lower limit of the dielectric loss tangent at a frequency of 10 GHz is not particularly limited. For example, resin sheets 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, 0.001 to 0.01, 0.001 to 0.0065, 0.001 to 0.0055, or 0.001 to 0.0045. However, these are 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. Resin sheets having a dielectric loss tangent at a frequency of 1 GHz in this range have high radio wave transmittance and are suitable for use in constructing electronic devices equipped with antennas. The lower limit of the dielectric loss tangent at a frequency of 1 GHz is not particularly limited. For example, resin sheets 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, 0.001 to 0.01, 0.001 to 0.009, or 0.001 to 0.008. However, these are examples of the dielectric loss tangent at a frequency of 1 GHz. The dielectric loss tangent at a frequency of 1 GHz is preferably measured at room temperature (e.g., 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-mentioned numerical ranges. In the resin sheet, 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-mentioned 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-mentioned numerical ranges.

[0077] [Density] The density of the resin sheet is 2 g / cm ３ It is preferable that the viscosity is 1.7 g / cm or less, for example. ３ The density of the resin sheet may be less than 1 g / cm. Various electronic devices configured with such a resin sheet mounted thereon are suitable for use in, for example, configuring portable electronic devices because heat generation is suppressed and the electronic devices are lightweight. The lower limit of the density of the resin sheet is not particularly limited. For example, ３ 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 at 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 an electron beam, the resin sheet is partially crosslinked, improving the heat resistance and repairability of the resin sheet.

[0080] <<Resin composition and manufacturing method thereof>> The resin sheet of the first aspect can be manufactured by using a resin composition (sometimes referred to in this specification as the “resin composition of the first aspect”) containing, for example, 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, not only a component capable of dissolving a solute in a solution but also a component that serves as a dispersion medium in a dispersion liquid is referred to as a "solvent."

[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 selected arbitrarily depending on the purpose, and is not particularly limited.

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

[0085] The resin composition can be produced by blending the thermoplastic resin, the flake filler, the linked 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 of mixing the components when blending is not particularly limited, and may be appropriately selected from known methods. The temperature and time when adding and mixing the components are not particularly limited as long as the blended components do not deteriorate, and can be adjusted appropriately.

[0086] The resin composition may be, for example, a kneaded product obtained by kneading (preferably melt-kneading) the thermoplastic resin, the platy filler, the connecting filler, and, if necessary, the other components.

[0087] <<Method for Producing Resin Sheet>> 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, 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, or a temperature 55°C or higher than the melting point of the thermoplastic resin. By setting the molding temperature at or above the lower limit, a more uniform resin sheet 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 pressurization is sufficient, but is preferably 3 MPa or more, and may be, for example, 8 MPa or more or 13 MPa or more. When the pressure is equal to or greater than the lower limit, 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 (pressure application time) of the resin composition is not particularly limited as long as the effect of pressure is sufficiently obtained, and can be set arbitrarily depending on the pressure during molding, for example, but is preferably 0.5 minutes or more. When the molding time is equal to or greater than the lower limit, 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, a resin sheet with higher uniformity can be obtained.

[0092] <<Resin Sheet (Second Aspect)>> A resin sheet according to a second aspect of the present invention includes a thermoplastic resin, a plate-like filler, and a connecting filler, and the connecting filler has an average particle diameter of 2 μm or less. Because the resin sheet according to the second aspect includes the plate-like filler and the connecting filler, it has high thermal conductivity and high heat dissipation properties both parallel to its surface and in its thickness direction. Furthermore, because the resin sheet according to the second aspect includes a thermoplastic resin, it has flexibility when heated. The resin sheet according to the second aspect may be the same as the resin sheet according to the first aspect, except that the embedding ratio R is not specified to 30% or more. By covering, or preferably embedding, a heat-generating element such as a CPU with the resin sheet according to the second aspect, a new heat dissipation structure can be configured in various electronic devices, resulting in a high heat-suppression effect in various electronic devices. Furthermore, the heat dissipation structure can be configured not only for CPUs but also for other devices equipped with a heat-generating element similar to a CPU, resulting in a high heat-suppression effect.

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

[0094] The resin sheet of the second aspect 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 are 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. These components contained in the resin sheet of the second embodiment exhibit 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 linked filler, and the other components contained in the resin sheet of the second embodiment may each be one type only, 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 case of the resin sheet of the first embodiment.

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

[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 reasons 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 diameter of the plate-like filler contained in the resin sheet of the second embodiment is preferably 5 μm or more for the same reasons as in the case of the resin sheet of the first embodiment, and may be 15 μm or less, for example, 5 to 15 μm. It 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 parts) of the plate-like filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of the plate-like filler in the resin sheet] / [total volume (volume parts) of the resin sheet] × 100) is preferably 10% by volume or more and 35% by volume or less, for the same reasons as in the case of the resin sheet of the first embodiment, and may be, for example, 10 to 35% by volume, and 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 The resin sheet of the second aspect to which flame retardancy has been imparted, such as the resin sheet containing a magnesium hydroxide filler, can satisfy, for example, grade 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 the connected filler to the content of the plate-like filler ([content of connected filler in resin sheet (parts by volume)] / [content of plate-like filler in resin sheet (parts by volume)] × 100) is, for the same reasons as in the case of the resin sheet of the first embodiment, preferably 60% by volume or more, and preferably 300% by volume or less, and may be 140% by volume or less, for example, may be any one of 60 to 300% by volume and 60 to 140% by volume, 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 (parts by volume) of the connected filler to the total volume (parts by volume) of the resin sheet ([content (parts by volume) of the connected filler in the resin sheet] / [total volume (parts by volume) 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, for example, is preferably 6% by volume or more and preferably 49% by volume or less, and may be, for example, 6 to 49% by volume, which may be 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 linked 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 linked filler in resin sheet (parts by mass)]) / [total mass of resin sheet (parts by mass)] × 100) may be in the same numerical range as in the case of the resin sheet of the first embodiment, for the same reasons as in the case of the resin sheet of the first embodiment, and is preferably 80% by mass or more and 100% by mass or less.

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

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

[0109] The 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 dielectric constant at a frequency of 10 GHz is preferably a value measured at room temperature (for example, under a temperature condition of 23°C).

[0110] The 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 dielectric constant at a frequency of 1 GHz is preferably a value measured at room temperature (for example, under a temperature condition of 23°C).

[0111] The dielectric loss 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 preferably 0.01 or less for the same reasons as in the case of the resin sheet of the first embodiment, 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, under a temperature condition of 23°C).

[0112] The dielectric loss 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 preferably 0.01 or less for the same reasons as in the case of the resin sheet of the first embodiment, 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, under a temperature condition 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-mentioned 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-mentioned 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 loss tangent at a frequency of 10 GHz, and the dielectric loss tangent at a frequency of 1 GHz are all within the above-mentioned numerical ranges.

[0114] The density of the resin sheet of the second embodiment is 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 1 g / cm or less. 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 permittivity, dielectric loss tangent and density of the resin sheet of the second embodiment can be adjusted 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, for example.

[0116] The flexibility of the resin sheet of the second embodiment when heated can be more easily adjusted by, for example, adjusting 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, it is possible to impart to the resin sheet of the second embodiment flexibility when heated similar to that of the resin sheet of the first embodiment in which the embedment ratio R is specified to be 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 under conditions of an absorbed dose of 20 to 300 kGy, and the acceleration voltage of the electron beam irradiation is preferably 100 to 300 kV.

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

[0119] The resin composition of the second embodiment can be produced by the same method 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 aspect can be manufactured by the same method as the resin sheet of the first aspect described above, except that the resin composition of the second aspect is used instead of the resin composition of the first aspect. For example, the molding temperature (pressure temperature) of the resin composition of the second aspect 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 aspect, and may be 15 ° C or 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, and may be in the same numerical range as in the case of the resin sheet of the first aspect.

[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 aspect and the resin sheet of the second aspect) to cover the surface of a heat generating element such as a CPU, a new heat dissipation structure can be configured in various electronic devices, and heat generation in the various electronic devices can be suppressed.

[0122] 2A and 2B are cross-sectional views schematically illustrating an example of a method of using the resin sheet (sometimes referred to herein as "method of use 1"). 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] 2A and 2B 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 Usage Method 1, first, as shown in FIG. 2A , a laminated structure 101 is prepared, which is constructed by stacking a resin sheet 1, a heat spreader 4, and a housing 3 in this order in the thickness direction. The resin sheet 1 is the resin sheet of the present 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 as desired depending on the purpose. Examples of materials constituting the housing 3 include resin, metal, and carbon material. The heat spreader 4 is also known, and examples of materials thereof include metals such as copper; carbon materials such as graphite; and the like.

[0125] There are no particular limitations on the circuit board 7, and it 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 connecting portion 6.

[0126] Thickness T of resin sheet 1 ｘ is preferably in the numerical range described above. 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 more easily covered. ｘ When T is equal to or less than the upper limit, the thickness of the resin sheet 1 can be prevented 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. ｘ However, even if the thickness of the resin sheet 1 is less than one time the height (thickness) of the object to which the resin sheet 1 is applied, the object can be sufficiently embedded in the resin sheet 1. ｘIt is preferable that the thickness of the object to be applied satisfies the numerical range described above and also satisfies the numerical range based on the height of the object to be applied. If the height (thickness) of the object to be applied is not constant, the height at the highest part (the thickness at the thickest part) is taken as the height (thickness) of the object to be applied.

[0127] Here, the object to which the resin sheet 1 is applied is, for example, the heating element 5 and the connecting portion 6 when the resin sheet 1 covers the entire exposed surface of the heating element 5 and the entire exposed portion of the connecting portion 6, and the height thereof is indicated by the symbol T in FIG. ｙ In contrast to this, for example, if the resin sheet 1 covers the entire exposed surface of the heating element 5 but does not cover the connection portion 6, the object to which the resin sheet 1 is applied is the entire area of ​​the heating element 5. For example, if the resin sheet 1 covers only a portion of the exposed surface of the heating element 5, the object to which the resin sheet 1 is applied 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 heating element 5 with the resin sheet 1 facing the heating element 5 (in other words, with the housing 3 facing away from the heating element 5). In other words, one surface 1 a of the resin sheet 1 and the exposed surface 5 a of the heating element 5 face each other.

[0129] In the first method of use, the laminated structure 101 is then １ , and press the resin sheet 1 against the heating element 5, or move the heating element 5 on the circuit board 7 together with the circuit board 7 in the direction of arrow P ２ , and the heating element 5 is pressed against the resin sheet 1, or the laminated structure 101 is moved in the direction of the arrow P １ , and the heating element 5 on the circuit board 7 is moved in the direction of the arrow P ２2B , 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. 2B . 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 then another area of ​​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 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] 2A and 2B show a state in which one heating element 5 is provided on one surface 7a of the circuit board 7, but the number of heating elements provided on one surface 7a of the circuit board 7 may be only one or two or more. When two or more heating elements are provided on one surface 7a of the circuit board 7, these two or more heating elements may be the same or different. That is, 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 together by a single resin sheet 1, as described above, all of the heating elements can be easily and sufficiently covered by a single resin sheet 1 by bringing other areas of one surface 1a of the resin sheet 1 into contact with one surface 7a of the circuit board 7 or bringing it close to the one surface 7a of the circuit board 7.

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

[0133] When covering the heating element 5 with the resin sheet 1 (embedding the heating element 5 in FIG. 2B ), 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 (a 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 increased. 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. 2B ), 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 more uniformly covered with the resin sheet 1. When the pressure is equal to or less than the upper limit, excessive pressure can be avoided. Because the resin sheet 1 has high flexibility when heated, it can sufficiently 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, resulting in a high degree of adhesion between the resin sheet 1 and the heating element 5, and a high degree of 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 surface direction D Ｓ The heat generated by the heating element 5 is conducted along the thickness direction D in the resin sheet 1 and is then radiated to the atmosphere, for example. ＴThe heat is conducted along the thickness direction D and dissipated into the atmosphere via 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 Furthermore, the heat dissipation in the thickness direction D of the resin sheet 1 is improved. Ｔ The heat conducted along the thickness direction D of the resin sheet 1 may be dissipated into the atmosphere via the circuit board 7. When the housing 3 is made of a highly thermally conductive material such as a metal or a carbon material, the heat conducted along the thickness direction D of the resin sheet 1 may be dissipated into the atmosphere via the circuit board 7. Ｔ The heat conducted along the heat spreader 4 is dissipated into the atmosphere not only through the heat spreader 4 but also through the housing 3. 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 heat dissipation properties in both the surface direction and the thickness direction, and also has high flexibility when heated. Such a heat dissipation structure via the resin sheet 1 in Usage Method 1 is completely unprecedented in conventional heat dissipation structures.

[0138] 3A and 3B are cross-sectional views schematically showing 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 in this specification as "method of use 2"). Here, an example is shown in which the resin sheet covers only a part of the exposed surface of the heating element, i.e., the heating element is not embedded.

[0139] 3A, 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 region having a height T ｙ is different from that in the case of Usage Method 1.

[0140] In Usage Method 2, the heating element 5 is then covered with the resin sheet 1 as shown in Fig. 3B in the same manner as Usage Method 1. 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 portion 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, and therefore, similar to the case of usage method 1, the degree of adhesion between the resin sheet 1 and the heating element 5 is high. More specifically, the generation 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 is reached by the resin sheet 1 in the thickness direction of the resin sheet 1, and it is also possible to eliminate the presence of this gap (to completely prevent the generation of this gap) by adjusting the conditions when the heating element 5 is covered with the resin sheet 1.

[0142] As described above, except for the fact that the object to which the resin sheet 1 is applied is 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 Usage Methods> The usage methods of the resin sheets (the resin sheet of the first embodiment and the resin sheet of the second embodiment) are not limited to Usage Method 1 and Usage Method 2, and for example, in Usage Method 1 or Usage Method 2, some components may be changed, deleted, or added.

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

[0145] For example, there may be a gap between one side of the resin sheet (the side facing the circuit board, for example, one side 1a of the resin sheet 1 in Figure 3B) and the exposed side of the heating element (for example, exposed side 5a of the heating element 5 in Figure 3B), and between one side of the resin sheet (the side facing the circuit board, for example, one side 1a of the resin sheet 1 in Figure 3B) and the connection portion (for example, connection portion 6 in Figure 3B).

[0146] As explained above, the resin sheet of this embodiment has excellent flexibility when heated, allowing it to cover, and preferably embed, a heat-generating element. Therefore, the resin sheet of this embodiment has extremely excellent heat dissipation properties. In contrast, conventional heat-dissipating sheets, such as graphite sheets, have excellent heat dissipation properties, but lack conformability to the object being cooled and insufficient adhesion to the object being cooled, making them unsuitable as a heat-dissipating structure to be installed alone on a heat-generating element. Furthermore, heat-dissipating sheets such as graphite sheets are also conductive, and due to their conductivity (lack of insulation), they cannot be used in the vicinity of an antenna. For example, thermal interface materials (TIMs) have adhesion to the object being cooled and are insulating, but their heat dissipation and conformability to the object being cooled are insufficient. For example, heat-dissipating materials that are liquid at room temperature are known, but their use is limited to enclosed spaces, and the filling process is cumbersome and their repairability is poor. The resin sheet of this embodiment can solve all of these conventional problems.

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

[0148] [Thermoplastic resin] Thermoplastic resin (a1): Ethylene-vinyl acetate copolymer (EVA) (manufactured by 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 at a temperature of 190° C. under a load of 2.16 kg.

[0149] [Plate-like filler] Plate-like filler (b1): Plate-like boron nitride filler ("K03" manufactured by Tokuyama Corporation, average particle diameter 9 μm, density 2.3 g / cm ３ , thermal conductivity 60 W / m·K, aspect ratio 30, relative dielectric constant 4)

[0150] [Linked Filler] Linked filler (c1): magnesium hydroxide filler surface-treated with a 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). Linked filler (c4): Magnesium hydroxide filler ("KISUMA (registered trademark) 5" manufactured by Kyowa Chemical Industry Co., Ltd., average particle size 0.83 μm, thermal conductivity 8 W / m·K). Linked filler (c5): Magnesium hydroxide filler ("KISUMA (registered trademark) 8" manufactured by Kyowa Chemical Industry Co., Ltd., average particle size 1.38 μm, thermal conductivity 8 W / m·K).

[0151] [Other fillers] Other fillers (d1): card-house-shaped aluminum oxide filler ("AC75" manufactured by DIC Corporation, average particle diameter 70 μm, density 3.97 g / cm ３ , thermal conductivity 20 W / m K) Other filler (d2): Polyhedral aluminum oxide filler (DIC Corporation "AH40-S", average particle size 32 μm, density 3.97 g / cm３ , thermal conductivity 20 W / m K)

[0152] [Example 1] <<Production of Resin Sheet>> 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. The resulting resin composition was sandwiched between a pair of hot plates and molded by vacuum hot pressing at a pressure of 15 MPa for 1 minute while heating at 120°C under vacuum conditions of a pressure of 0.02 MPa or less, to obtain a single-layer resin sheet (thickness 700 μm).

[0153] <<Evaluation of Resin Sheets>> <Calculation of Embedding R> Three resin sheets (700 μm thick) obtained by the above method were stacked in the thickness direction and cut into a size of 3.5 cm×3.5 cm to obtain a thickness T ０ A test specimen with a diameter of 2100 μm and a rectangular planar shape was prepared. Next, the obtained test specimen was placed on a flat surface, and a ceramic cylindrical indenter with a diameter of 16 mm and a height of 14 mm was placed near the center of the upward exposed surface of the test specimen. At this time, one flat surface of the indenter, rather than the curved surface, was in contact with the exposed surface of the test specimen. Furthermore, a weight was placed on the entire other flat surface of the indenter in this state (the upward exposed surface not in contact with the exposed surface of the test specimen). In this way, by stacking the test specimen, indenter, and weight in this order, a pressure of 12 kPa was applied to the test specimen in its thickness direction. The stack was then immediately transferred to an environment at 100°C and left to stand for 10 minutes. As a result, a pressure of 12 kPa was applied to the test specimen in its thickness direction in an environment at 100°C for 10 minutes. Then, immediately after 10 minutes, the thickness T of the test piece at the part of the laminate in this state where pressure was applied was measured. １ The embedding ratio R of the test piece (resin sheet) was then calculated using the above formula. The results are shown in Table 1.

[0154] <Confirmation of Heat Dissipation Property of Resin Sheet (1)> The resin sheet (thickness: 700 μm) obtained above was cut into a size of 10 cm×10 cm.

[0155] Four resistors were arranged in a row on the circuit surface of the circuit board at approximately equal intervals. These four resistors were given the symbols (1-1) to (1-4) from one end of the row to the other. Furthermore, in a direction perpendicular to the row, a separate resistor was arranged on the same side as these four resistors (i.e., resistor (1-1), resistor (1-2), resistor (1-3), and resistor (1-4)) and approximately equidistant from each of these four resistors. These four separately arranged resistors were given the symbols (2-1) to (2-4) from one end of the row to the other. Resistor (2-1) is adjacent to resistor (1-1) but not resistor (1-4), resistor (2-2) is adjacent to resistor (1-2) but not resistor (1-3), resistor (2-3) is adjacent to resistor (1-3) but not resistor (1-2), and resistor (2-4) is adjacent to resistor (1-4) but not resistor (1-1). As a result, 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 spacing between adjacent resistors in two orthogonal directions was approximately equal. The height of these eight resistors (i.e., the distance between the top surface of the resistor (the surface opposite the circuit board) and the circuit surface of the circuit board) was approximately 4 mm. Figure 4 shows a plan view schematically illustrating the arrangement of the resistors on the circuit board at this time.

[0156] Next, of the four resistors in one row, one thin-wire thermocouple was placed for each of the two resistors at both ends (resistor (1-1) and resistor (1-4)). Furthermore, of the four resistors in the other row, one thin-wire thermocouple was placed for each of the second resistor from one end (resistor (2-2)). Then, one thin-wire thermocouple was placed in a location on the circuit surface of the circuit board that was midway between these two rows and also approximately the center in the row direction of these two rows (approximately the center on the circuit surface of the circuit board), where no resistors were 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 resistors. The placement positions of the thermocouples in this case are also shown in Figure 4.

[0157] Next, for each of the eight resistors on the circuit surface, a sheet of thermal interface material (TIM, "Thermo-Trans H2" manufactured by Widework Corporation, 500 μm thick) was laminated on the entire surface opposite the circuit board side. This was done to prevent errors in the height of the eight resistors from affecting the evaluation results, as the heights of the eight resistors were not all strictly the same. As a result, the thermocouples on the resistors were positioned between the resistors and the thermal interface material (TIM) sheet. Furthermore, the entire surface of each of the thermal interface material sheets opposite the resistor side was collectively covered with the resin sheet (700 μm thick) obtained above. Furthermore, a polycarbonate substrate (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 way, a test circuit board for evaluating the heat dissipation properties of the resin sheet was prepared.

[0158] A thermograph was placed on top 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 substrate was measured using the 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.

[0159] <Measurement of thermal conductivity in the plane direction of resin sheet> The thermal conductivity of the resin sheet obtained above was measured in the plane direction using a hot disk method thermal property measuring device ("TPS 500 S" manufactured by Kyoto Electronics Manufacturing Co., Ltd.). At this time, two resin sheets were sandwiched between insulating materials, and a sensor with a diameter of 7 mm was inserted between the resin sheets to measure the thermal conductivity of the resin sheet. The results are shown in Table 1.

[0160] <Measurement of relative permittivity and dielectric loss tangent of resin sheet> Test pieces of a predetermined size were cut out from the resin sheet obtained above at room temperature, and the relative permittivity and dielectric loss tangent at frequencies of 1 GHz and 10 GHz of these test pieces were measured in accordance with the TM0m0 mode cavity resonator perturbation method. The results are shown in Table 1.

[0161] <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.

[0162] <<Production and Evaluation of Resin Sheets>> [Comparative Example 1] A pellet-shaped resin composition was prepared 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 (700 μm thick) 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 obtained when checking the heat dissipation properties of the resin sheet in this comparative example.

[0163] [Comparative Example 2] A pellet-shaped resin composition was prepared 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 (700 μm thick) 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 obtained when checking the heat dissipation properties of the resin sheet in this comparative example.

[0164] <<Evaluation of Test Resin Sheets>> <Confirmation of Heat Dissipation Properties of Test Resin Sheets> [Test Example 1] A commercially available thermally conductive sheet (500 μm thick) 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. Eight resistors and four thermocouples were placed on the circuit surface of the circuit board using the same method as in "Confirmation of Heat Dissipation Properties of Resin Sheets" in Example 1. Next, for all eight resistors on the circuit surface, a sheet of thermal interface material (TIM, "Thermo-Trans H2" manufactured by Widework Corporation, 500 μm thick) was laminated on the entire surface opposite the circuit board side, if a thermocouple was placed, for each resistor. 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 each of these thermal interface material sheets opposite the resistor side was collectively covered with the above-mentioned test resin sheet (thickness: 500 μm). Furthermore, a polycarbonate substrate (thickness: 2000 μm) was placed on the entire surface of the covered test resin sheet opposite the thermal interface material sheet side. In this manner, a test circuit board was prepared for evaluating the heat dissipation properties of the test resin sheet. Subsequently, a voltage was applied to the test circuit board in the same manner as in Example 1, and the surface temperature of the polycarbonate substrate was measured using a thermograph. The image data obtained at this time is shown in FIG. 8. Furthermore, the temperatures detected by thermocouples on the resistor and circuit surfaces are shown in Table 1.

[0165] In Table 1, "platy filler content (volume %)" means the ratio of the content (volume parts) of the plate-like filler to the total volume (volume parts) of the resin sheet. Similarly, "connected filler content (volume %)" means the ratio of the content (volume parts) of the connected filler to the total volume (volume parts) of the resin sheet. "Ratio (volume %) of the connected filler to the content (volume parts) of the plate-like filler" means the ratio of the content (volume parts) of the connected filler to the content (volume parts) of the plate-like filler in the resin sheet. These also apply to Table 1 and subsequent tables.

[0166]

[0167] 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 during heating was high. Furthermore, as shown in Figure 5, the surface of the polycarbonate substrate was heated to approximately 65 to 85°C in the area where four resistors in the same row were present, spanning these resistors, and this was similar in the area where two rows were present. Furthermore, the area between these two rows was also heated to approximately 60 to 65°C. This indicates that the resin sheet dissipated the heat generated from the four resistors in the same row not only in the length direction of the row but also in the width direction of the row, demonstrating that the resin sheet has high heat dissipation properties in its surface direction. Meanwhile, as shown in Table 1, when the temperatures detected by 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 higher heat dissipation properties not only in its surface direction but also in its thickness direction than the test resin sheet of Test Example 1 (a commercially available thermally conductive sheet). In the above evaluation, the heat dissipation properties of the resin sheet from the heating element (resistor) were simply confirmed without embedding the heating element in the resin sheet. However, it was speculated that the resin sheet of Example 1 would also exhibit high heat dissipation properties by covering the heating element over a wider area, preferably by embedding it. Thus, it was confirmed that the resin sheet of Example 1 has high flexibility when heated and high heat dissipation properties in both its surface direction and thickness direction, making it possible to configure a new heat dissipation structure. The resin sheet of Example 1 contained a thermoplastic resin, a plate-like filler, and a connecting filler. Furthermore, in the sheet of Example 1, the ratio of the connecting filler content to the plate-like filler content was 72.0% by volume.

[0168] The relative dielectric constant of the resin sheet of Example 1 was less than 4 at both frequencies of 1 GHz and 10 GHz. The dielectric loss tangent of the resin sheet of Example 1 was 0.01 or less at both frequencies of 1 GHz and 10 GHz. The density of the resin sheet of Example 1 was 2 g / cm ３ It was less than.

[0169] In contrast, in Comparative Example 1, the embedding ratio R was low at 11.0%, and the flexibility of the resin sheet during heating was low, so the resin sheet was unable to cover, or preferably embed, the heating elements over a wider area. Furthermore, as shown in Figure 6, the surface of the polycarbonate substrate was heated to approximately 65 to 85°C in the area where four resistors in the same row were present, spanning these resistors. This was similar in the area where two rows were present, but the area where such heat was present was narrower than in Example 1. The area between these two rows was not highly heated. This indicates that although the resin sheet dissipated the heat generated from the four resistors in the same row in the length direction of the row, 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. This indicates 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 detected temperatures by 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 properties than the test resin sheet of Test Example 1 (a commercially available thermally conductive sheet). Thus, the resin sheet of Comparative Example 1 had low flexibility when heated and low heat dissipation properties in both the surface direction and the thickness direction. The resin sheet of Comparative Example 1 contained a connecting filler but did not contain a plate-like filler. Instead, it contained another filler (d1). The other filler (d1) was card-house shaped and consisted of spherical aggregates of plate-like aluminum oxide.

[0170] In Comparative Example 2, the embedding ratio R was high at 49.5%, and the flexibility of the resin sheet during heating was high. As shown in Figure 7, the surface of the polycarbonate substrate was heated to approximately 65 to 85°C in the area where four resistors in the same row were present, spanning these resistors. This was similar 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 indicated 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. Meanwhile, as shown in Table 1, when the temperatures detected by thermocouples for the same resistors were compared between Comparative Example 2 and Test Example 1, the detected temperatures in Comparative Example 2 were all higher than those in Test Example 1, as in Comparative Example 1. 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 of Comparative Example 2 had lower heat dissipation properties than the resin sheet of Comparative Example 1. Thus, the resin sheet of 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.

[0171] The relative dielectric constant of the resin sheets of Comparative Examples 1 and 2 exceeded 4 at both frequencies of 1 GHz and 10 GHz. The density of the resin sheets of Comparative Examples 1 and 2 was 2 g / cm ３ It exceeded that.

[0172] The test resin sheet in Test Example 1 (a commercially available thermally conductive sheet) lacked flexibility when heated and was unable to cover or embed a wider area of ​​the heat-generating element. In Test Example 1, as shown in FIG. 8 , the surface of the polycarbonate substrate was heated to approximately 60 to 80°C in the area where four resistors in the same row were present, spanning these resistors. This was also the case in the area where two rows were present. However, in Test Example 1, this heated area was narrower than in Example 1. Furthermore, the area between these two rows was not highly heated. These results indicated that the resin sheet in Test Example 1 had lower heat dissipation properties 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 properties than the resin sheet in Example 1.

[0173] Example 2 <<Production of Resin Sheet>> A single-layer resin sheet (thickness: 1500 μm) was produced in the same manner as in Example 1, except that the amount of the pellet-shaped resin composition used was changed. That is, the resin sheet of this example differed from the resin sheet of Example 1 only in its thickness.

[0174] <<Evaluation of Resin Sheet>> <Confirmation of Heat Dissipation Property of Resin Sheet (2)>> The resin sheet (thickness: 1500 μm) obtained above was cut into a size of 10 cm×10 cm.

[0175] A circuit board equipped with resistors and thermocouples, the same as in Example 1 (shown in FIG. 4), was prepared. Next, for all eight resistors on the circuit surface, the entire surface opposite the circuit board side was collectively covered with the resin sheet (thickness: 1500 μm) obtained above, via the thermocouples, if any, and pressed. As a result, the thermocouples on the resistors were positioned between the resistors and the resin sheet. Furthermore, a polycarbonate substrate (thickness: 2000 μm) was placed on the entire surface of the resin sheet opposite the resistor side after covering. In this way, a test circuit board for evaluating the heat dissipation properties of the resin sheet was prepared.

[0176] In this test circuit board, the distance between the resistor-side surface of the polycarbonate substrate and the resistor-side surface of the polycarbonate substrate was measured for each of the eight resistors and found to be approximately 400 μm. Therefore, the embedding distance of the resin sheet in the area covering the resistors was approximately 1100 μm (= 1500 μm - 400 μm).

[0177] A thermograph was placed on the top 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 a voltage was applied to the test circuit board. Under these conditions, the temperature of the surface of the polycarbonate substrate was measured using the 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.

[0178] <<Evaluation of Resin Sheet>> <Confirmation of Heat Dissipation Property of Resin Sheet (2)> [Example 1] The heat dissipation property of the resin sheet (thickness 700 μm) of Example 1 was confirmed by the same method as in Example 2. The temperatures detected by the thermocouple at this time are shown in Table 2.

[0179] In the test circuit board used in this example, the distance between the resistor side of the polycarbonate substrate and the resistor side facing the polycarbonate substrate was measured for each of the eight resistors and found to be approximately 400 μm. Therefore, the embedding distance of the resin sheet in the area covering the resistor was approximately 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) of the polycarbonate substrate was the same as in Example 2.

[0180] <<Confirmation of resistor temperature without resin sheet>> [Test example 2] A test was performed in the same manner as in Example 2, except that a resin sheet was not used, and the temperature detected by the thermocouple was confirmed. The results are shown in Table 2.

[0181] <<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 all eight resistors on the circuit surface opposite the circuit board side was collectively covered with a single thermal interface material sheet, via a thermocouple if one was placed therein. 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 the same as in Example 2. The temperatures detected by the thermocouples at this time are shown in Table 2. In this test example, the thermocouples on the resistors were placed between the resistors and the thermal interface material. The results are shown in Table 2.

[0182]

[0183] As is clear from the above results, when the temperatures detected by thermocouples between the same resistors and the same 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 in Test Example 2. This was because Test Example 2 did not have a heat dissipation structure. Furthermore, when the temperatures detected by thermocouples between the same resistors and 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 in Test Example 3. This indicated that the resin sheets of Examples 1 and 2 had 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. In the above evaluation, the heat dissipation ability 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 2 would also exhibit high heat dissipation ability 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 ability in both the surface direction and the thickness direction, and is capable of configuring a new heat dissipation structure.

[0184] 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 in Example 1, and therefore the heat dissipation effect of the resin sheet was higher.

[0185] [Example 3] <<Production of Resin Sheet>> A single-layer resin sheet (thickness 1541 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.

[0186] <<Evaluation of Resin Sheet>> <Calculation of Embedding Ratio R> For the resin sheet obtained above, the embedding ratio R was calculated in the same manner as in Example 1. The results are shown in Table 3.

[0187] <Confirmation of Heat Dissipation Property of Resin Sheet (3)> The resin sheet (thickness: 1500 μm) obtained above was cut into a size of 5 cm×5 cm.

[0188] A resistor was placed on the circuit surface of the circuit board. The height of this resistor (i.e., the distance between the top surface of the resistor (the surface opposite the circuit board) and the circuit surface of the circuit board) was 1.2 mm. Next, a thin-wire thermocouple was placed on this resistor. Furthermore, a thin-wire thermocouple was placed on the surface opposite the circuit surface of the circuit board (the back surface) at a position directly below the resistor.

[0189] Next, the entire surface of the resistor on the circuit surface opposite the circuit board side was covered with a resin sheet (thickness 1500 μm) obtained above via a thermocouple and pressed. As a result, the thermocouple on the resistor was positioned between the resistor and the resin sheet. Furthermore, a polycarbonate substrate (thickness 2000 μm) was placed on the entire surface of the resin sheet opposite the resistor side after this covering. This resulted in a test circuit board for evaluating the heat dissipation properties of the resin sheet.

[0190] In this test circuit board, the distance between the resistor-side surface of the polycarbonate substrate and the resistor-side surface of the polycarbonate substrate was approximately 400 μm. In this test circuit board, the area of ​​the resin sheet's surface 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.

[0191] A thermograph was placed on the top 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 a voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate substrate was measured using the thermograph. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0192] <Measurement of thermal conductivity, relative dielectric constant, dielectric loss tangent, and density in the plane direction of the resin sheet> The thermal conductivity, relative dielectric constant, dielectric loss tangent, and density of the resin sheet obtained above were measured in the same manner as in Example 1. The results are shown in Table 3.

[0193] [Example 4] <<Production of Resin Sheet>> A single-layer resin sheet (thickness 1550 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.

[0194] <<Evaluation of Resin Sheet>> <Calculation of Embedding Ratio R> For the resin sheet obtained above, the embedding ratio R was calculated in the same manner as in Example 1. The results are shown in Table 3.

[0195] <Confirmation of Heat Dissipation Property of Resin Sheet (3)> The heat dissipation property of the resin sheet obtained above was confirmed in the same manner as in Example 3. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0196] In the test circuit board used in this example, the distance between the resistor-side surface of the polycarbonate substrate and the resistor-side surface of the polycarbonate substrate was approximately 400 μm. As in Example 3, in this test circuit board, 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.

[0197] <Measurement of thermal conductivity, relative dielectric constant, dielectric loss tangent, and density in the plane direction of the resin sheet> The thermal conductivity, relative dielectric constant, dielectric loss tangent, and density of the resin sheet obtained above were measured in the same manner as in Example 1. The results are shown in Table 3.

[0198] <<Confirmation of resistor temperature without resin sheet>> [Test example 4] A test was performed in the same manner as in Example 3, except that a resin sheet was not used, and the temperature detected by the thermocouple was confirmed. The results are shown in Table 3.

[0199] <<Confirmation of Heat Dissipation Properties of Thermal Interface Material Sheet>> [Test Example 5] A circuit board equipped with a resistor and a thermocouple similar to that in Example 3 was prepared. Next, the entire surface of the resistor on the circuit surface opposite the circuit board side was covered with a single thermal interface material (TIM) sheet similar to that used in Test Example 1 via a thermocouple, and pressed. That is, in this test example, unlike 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 positioned 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 the resistor side after this covering. In this way, a test circuit board for evaluating the heat dissipation properties of a 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.

[0200] A thermograph was placed on the top 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 a voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate substrate was measured using the thermograph. The temperatures detected by the thermocouple at this time are shown in Table 3.

[0201]

[0202] As is clear from the above results, when comparing the temperatures detected by thermocouples between resistors and between the back surfaces of the circuit boards in Examples 3 to 4 and Test Example 4, the detected temperatures in Examples 3 to 4 were significantly lower than in Test Example 4. This was because Test Example 4 did not have a heat dissipation structure. Furthermore, when comparing the temperatures detected by thermocouples between resistors and between the back surfaces of the circuit boards in Examples 3 to 4 and Test Example 5, the detected temperatures in Examples 3 to 4 were lower than in Test Example 5. This indicated that the resin sheets of Examples 3 to 4 had 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 compared to the resin sheets of Examples 3 to 4. Thus, it was confirmed that the resin sheets of Examples 3 to 4 had high flexibility when heated and high heat dissipation properties in both the surface direction and the thickness direction, making it possible to configure a new heat dissipation structure.

[0203] Furthermore, when the temperatures detected by the thermocouples between the resistors and between the back surfaces of the circuit boards in Example 3 and Example 4 were compared, 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.

[0204] The resin sheets of Examples 3 and 4 contained a thermoplastic resin, a plate-like filler, and a connecting filler. In the sheets of Examples 3 and 4, the ratio of the content of the connecting filler to the content of the plate-like filler was 99.1 to 296.6 volume %.

[0205] 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).

[0206] The relative dielectric constant of the resin sheets of Examples 3 and 4 was 4 or less at both frequencies of 1 GHz and 10 GHz. The dielectric loss tangent of the resin sheets of Examples 3 and 4 was less than 0.01 at both frequencies of 1 GHz and 10 GHz. The density of the resin sheets of Examples 3 and 4 was 2 g / cm ３ It was less than.

[0207] 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; it can also be used to configure a heat dissipation structure in other devices equipped with the same heat generating element as a CPU.

[0208] DESCRIPTION OF SYMBOLS 1: Resin sheet 3: Housing 4: Heat spreader 5: Heat generating element 6: Connection part 7: Circuit board 8: Weight 9: Indentation 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 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 diameter 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 of the test piece at the part where the pressure was applied was measured. １ When the measurement was performed, the following formula: R = (T ０ -T １ ) / T ０ x 100, the embedment rate R is 30% or more.

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

4. A resin sheet according to claim 1 or 3, wherein the dielectric tangent of the resin sheet at a frequency of 10 GHz, measured in accordance with a TM0m0 mode cavity resonator perturbation method, is 0.01 or less.

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

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

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

8. The resin sheet according to claim 1 or 3, wherein the ratio of the content of said connecting filler to the content of said plate-like filler in said resin sheet is 60 to 140 volume %.

9. The resin sheet according to claim 1 or 3, wherein the average particle size of the flake-like filler is 5 μm or more.

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

11. A resin sheet according to claim 2 or 10, wherein the dielectric tangent of the resin sheet at a frequency of 10 GHz, measured in accordance with a TM0m0 mode cavity resonator perturbation method, is 0.01 or less.

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

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

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

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

16. The resin sheet according to claim 2 or 10, wherein the average particle size of the plate-like filler is 5 μm or more.

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