resin sheet

Abstract

To provide a novel resin sheet that can be used to construct a new heat dissipation structure with high heat dissipation efficiency. [Solution] A resin sheet comprising a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle diameter of the connecting filler is 2 μm or less. Using a single resin sheet or a laminate of two or more resin sheets, and with a thickness T0, a pressure of 12 kPa is applied to the test sheet 10 in the thickness direction for 10 minutes in an environment of 100°C, and the thickness T1 of the test sheet 10 at the pressure applied is measured, and the following formula is obtained: R = (T0 - T1) / T0 × 100 The embedding rate R calculated by this method may be 30% or more.

Description

[Technical Field]

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

[0002] The central processing unit (CPU) is one of the representative devices that make up a computer. The amount of heat generated by the CPU increases dramatically when the computer is in operation. In recent years, with the increasing performance, miniaturization, and weight reduction of electronic devices, the density of semiconductor packages has increased, the integration of LSIs has increased, and the processing speed has increased, making countermeasures against the heat generated in electronic devices 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 (TIM), and this heat spreader is positioned in contact with a heat sink. As a result, in electronic devices, heat generated by the CPU is conducted to the heat spreader via the TIM, and further heat is conducted in the planar direction by this 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] Traditionally, the reasons for employing such a heat dissipation structure for CPUs are as follows: Heat spreaders are made of metal or graphite, and while they have high thermal conductivity in the planar direction and high heat dissipation, they do not conform to the object being cooled (CPU), their contact with the object being cooled (CPU) is insufficient, and they do not have insulating properties. On the other hand, TIMs have a certain degree of conformability to the object being cooled (CPU), good contact, and insulating properties, but their thermal conductivity is insufficient. Therefore, by using these (heat spreaders and TIMs) in combination and adopting the heat dissipation structure described above, these shortcomings are compensated for. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 139364 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in conventional electronic devices, as long as TIM is a mandatory component, the heat dissipation structure is limited, and the configuration of the electronic device is also limited. Considering the need for insulation and flexibility, a resin sheet would be appropriate as an alternative to TIM, but a resin sheet with high heat dissipation efficiency has not been known until now. While I've used the CPU as an example so far, similar problems can occur with other devices that have heat-generating components similar to those in a CPU.

[0007] The object of this invention is to provide a novel resin sheet that can be used to construct a new heat dissipation structure with high heat dissipation effect. [Means for solving the problem]

[0008] This invention employs the following configuration. [1] A resin sheet comprising a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle diameter of the connecting filler is 2 μm or less. [2] A resin sheet comprising a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle diameter of the connecting filler is 2 μm or less, and the test specimen is one resin sheet or a laminate of two or more resin sheets, and a pressure of 12 kPa is applied to the test specimen in the thickness direction for 10 minutes in an environment of 100°C, and the thickness T1 of the test specimen at the pressure applied is measured, and the following formula is obtained: R = (T0 - T1) / T0 × 100 A resin sheet in which the embedding rate R calculated by the following formula is 30% or more.

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

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

[0011]

[10] The resin sheet according to [2], wherein the relative permittivity of the resin sheet at a frequency of 10 GHz, measured in accordance with the 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 the 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 connecting filler to the content of the plate-like filler in the resin sheet is 60 to 140% by volume.

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

[10] to

[15] , wherein the average particle diameter of the plate-like filler is 5 μm or more. [Effects of the Invention]

[0012] According to the present invention, a novel resin sheet capable of forming a new heat dissipation structure having a high heat dissipation effect is provided. [Brief Description of the Drawings]

[0013] [Figure 1] It is a cross-sectional view for schematically explaining a method for calculating the embedding rate R of a test piece using the resin sheet according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of a method of using the resin sheet according to an embodiment of the present invention. [Figure 3] It is a cross-sectional view schematically showing another example of a method of using the resin sheet according to an embodiment of the present invention. [Figure 4] It is a plan view schematically showing the arrangement positions of a resistor and a thermocouple on a circuit board when confirming the heat dissipation property of the resin sheet or the test resin sheet with respect to the heating element in Example 1, Comparative Examples 1 to 2, and Test Example 1. [Figure 5] It is image data showing the confirmation result of the heat dissipation property of the resin sheet with respect to the heating element in Example 1. [Figure 6] It is image data showing the confirmation result of the heat dissipation property of the resin sheet with respect to the heating element in Comparative Example 1. [Figure 7]This image data shows the results of the verification of the heat dissipation performance of the resin sheet relative to the heat-generating element in Comparative Example 2. [Figure 8] This image data shows the results of the confirmation of the heat dissipation performance of the test resin sheet against the heat-generating element in Test Example 1. [Modes for carrying out the invention]

[0014] <<Resin sheet (first embodiment)>> A resin sheet according to a first embodiment of one embodiment comprises a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle diameter of the connecting filler is 2 μm or less, and the resin sheet is a single sheet or a laminate of two or more sheets, and a test specimen with a thickness T0 is used, and a pressure of 12 kPa is applied to the test specimen in the thickness direction of the test specimen for 10 minutes in an environment of 100°C, and the thickness T1 of the test specimen at the pressure applied is measured, and the following formula is obtained: R = (T0 - T1) / T0 × 100 The embedding rate R calculated is 30% or more. The resin sheet of the first embodiment contains the plate-shaped filler and the connecting filler, and therefore has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and in its thickness direction. Furthermore, the resin sheet of the first embodiment contains a thermoplastic resin, and its embedding ratio R is 30% or more, and it has high flexibility when heated. By covering and preferably embedding a heat-generating element such as a CPU (central processing unit) with the resin sheet of the first embodiment having such characteristics, a new heat dissipation structure can be constructed in various electronic devices, and a high effect of suppressing heat generation in various electronic devices can be obtained. Moreover, it is not limited to CPUs, but a heat dissipation structure can also be constructed in other devices equipped with heat-generating elements similar to those of a CPU, and a high effect of suppressing heat generation can be obtained. In this specification, the term "direction parallel to the surface" may be used to refer to a direction parallel to the surface, not only in the case of resin sheets.

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

[0016] <Thermoplastic resin> The resin sheet, by containing the thermoplastic resin, can maintain a sheet-like shape and has conformability and adhesion to the 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 achieve the embedding ratio R.

[0018] The resin sheet can be manufactured, for example, by molding (pressure-heat molding) a resin composition, which will be described later, for manufacturing the resin sheet. In this case, it is preferable that the thermoplastic resin 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, 80°C or lower, or 70°C or lower. By using a thermoplastic resin with a melting point below 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, thermoplastic resins with a melting point of 35°C or higher are more readily available or can be manufactured. In one embodiment, the melting point of the thermoplastic resin may be, for example, 35-90°C, 35-80°C, or 35-70°C. However, these are just examples of melting points for 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 above the lower limit, the conformability of the resin sheet to the object to which it is applied is improved, for example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet. When the MFR of the thermoplastic resin is below the upper limit, the shape of the resin sheet can be maintained more stably. In this specification, unless otherwise specified, MFR refers to the value measured in accordance with JIS K 6922-1.

[0021] Preferred thermoplastic resins include, for example, ethylene-vinyl acetate copolymer (EVA). Ethylene-vinyl acetate copolymer has a lower melting point than other resins and exhibits endothermic properties at or near its melting point when heated. Therefore, the resin sheet containing ethylene-vinyl acetate copolymer has higher heat dissipation properties due to its latent heat storage function. In addition, ethylene-vinyl acetate copolymer has flexibility, impact resistance, and adhesive properties, so when a heating element is covered with the resin sheet containing ethylene-vinyl acetate copolymer, the resin sheet adheres easily to the heating element. Furthermore, because ethylene-vinyl acetate copolymer is polar, it can be compounded with flame retardants (for example, magnesium hydroxide, etc.), and flame retardancy can be easily imparted to the resin sheet.

[0022] In the ethylene-vinyl acetate copolymer, the ratio of the amount of constituent units derived from vinyl acetate (parts by mass) to the total amount of constituent units (parts by mass) (sometimes referred to as "vinyl acetate content" in this specification) 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 above the lower limit, the conformability and adhesion of the resin sheet to the object to which it is applied are improved. For example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet, and the resin sheet adheres easily to the heating element. When the ratio is below the upper limit, the workability during the manufacture of the resin sheet is improved.

[0023] The thermoplastic resin contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0024] The thermoplastic resin contained in the resin sheet is preferably an ethylene-vinyl acetate copolymer, in that the effects of the present invention are more pronounced.

[0025] In the resin sheet, the ratio of the thermoplastic resin content (parts by mass) to the total mass (parts by mass) of the resin sheet ([thermoplastic resin content (parts by mass) of 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 above the lower limit, the effect obtained by the resin sheet containing thermoplastic resin is further enhanced. In the resin sheet, the ratio of the thermoplastic resin content (parts by mass) to the total mass (parts by mass) of the resin sheet is preferably 45% by mass or less, and more preferably 40% by mass or less. When the ratio is below the upper limit, the effects obtained by the resin sheet containing components other than the thermoplastic resin are further enhanced. In one embodiment, the proportion may be, for example, 20-45% by mass, 25-45% by mass, and 30-45% by mass, or 20-40% by mass, 25-40% by mass, and 30-40% by mass. However, these are just examples of the proportions. The aforementioned ratio is typically the same as the ratio of the content of the thermoplastic resin (parts by mass) to the total content of components that do not vaporize at room temperature in the resin composition described later ([Content of thermoplastic resin in the resin composition (parts by mass)] / [Total content of components that do not vaporize at room temperature in the resin composition (parts by mass)] × 100).

[0026] In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0027] <Sheet-shaped filler> The resin sheet has improved heat dissipation due to the inclusion of the plate-shaped filler. The plate-shaped filler in the resin sheet 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. As a result, the thermal conductivity of the resin sheet in that surface direction becomes particularly high, and the heat dissipation in that surface direction becomes high. For example, if a filler other than a plate-shaped filler is used, such as a polyhedral filler or a card-house-shaped filler (a filler in which plate-shaped fillers aggregate to form secondary particles), the heat dissipation of the resin sheet in its planar direction will be reduced. Furthermore, card-house-shaped fillers significantly reduce 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, 10 to 30 and 30 to 50. Having the aspect ratio of the plate-like filler within this range enhances the effects obtained by the resin sheet containing the plate-like filler.

[0029] As the particle size of the plate-shaped filler, for example, the maximum length of the line segment connecting two different points on the outer circumference of the plate-shaped filler can be adopted. As the thickness of the plate-like filler, for example, the maximum distance between the main surfaces of the plate-like filler can be used. As the aspect ratio of the plate-shaped filler, for example, the average of the aspect ratios of 50 randomly selected plate-shaped fillers can be adopted.

[0030] The average particle diameter of the plate-shaped filler is preferably 5 μm or more, and may be, for example, 6.5 μm or more, or 8 μm or more. When the average particle diameter of the plate-shaped filler is above the lower limit, the effects obtained by using the plate-shaped filler are further enhanced. There is no particular upper limit to the average particle size of plate-shaped fillers. For example, plate-shaped fillers with an average particle size of 15 μm or less are more readily available. In one embodiment, the average particle size of the plate-shaped filler may be, for example, 5 to 15 μm, 6.5 to 15 μm, and 8 to 15 μm. However, these are just examples of average particle sizes for plate-shaped fillers.

[0031] In this specification, not only in the case of plate-shaped fillers, but unless otherwise specified, "average particle diameter" refers to the particle diameter at 50% accumulation of particles (D50) when the particle size distribution of the particles is measured on a volume basis by laser diffraction particle size distribution measurement.

[0032] The thermal conductivity of the plate-shaped filler may be, for example, 5 W / m·K or higher, 10 W / m·K or higher, 25 W / m·K or higher, and 40 W / m·K or higher. There is no particular upper limit to the thermal conductivity of the plate-shaped filler. For example, plate-shaped fillers with a thermal conductivity of 400 W / m·K or less are readily available. In one embodiment, the thermal conductivity of the plate-shaped filler may be, for example, 5 to 400 W / m·K, 10 to 400 W / m·K, 25 to 400 W / m·K, and 40 to 400 W / m·K. However, these are just examples of the thermal conductivity of the plate-shaped filler.

[0033] The thermal conductivity of fillers, not limited to plate-shaped fillers, can be measured, for example, by fabricating a sintered body of the filler and measuring it using a known thermal conductivity measuring device such as the laser flash method or the hot disk method, or by measuring it using a thermal property microscope or the like.

[0034] In order to more easily lower the dielectric constant of the resin sheet described later, the dielectric constant of the plate-shaped filler is preferably 5.5 or less, and more preferably 4.5 or less. On the other hand, the lower limit of the relative permittivity of the plate-shaped filler is not particularly limited. For example, plate-shaped fillers with a relative permittivity of 3.5 or higher are easier to prepare or obtain.

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

[0036] The plate-shaped filler contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0037] The plate-shaped filler is preferably made of boron nitride (BN) or aluminum oxide (Al2O3) (i.e., it is either a boron nitride filler or an aluminum oxide filler). A resin sheet containing such a plate-shaped filler has high heat dissipation properties, better fluidity when heated, and better conformability to the object to which the resin sheet is applied. For example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet.

[0038] The plate-shaped filler is more preferably made of boron nitride (BN) (i.e., a boron nitride filler). In addition to having the above-mentioned desirable properties, a resin sheet containing such a plate-shaped filler has even more desirable properties, as described later, because its dielectric constant is lower.

[0039] In the resin sheet, the ratio of the content (volume) of the plate-shaped filler to the total volume (volume) of the resin sheet ([content (volume) of the plate-shaped filler in the resin sheet] / [total volume (volume) of the resin sheet] × 100) is preferably 10 volume% or more, and may be, for example, 15 volume% or more, 20 volume% or more, or 25 volume% or more. When the ratio is above the lower limit, the effect obtained by using the plate-shaped filler is further enhanced. In the resin sheet, the ratio of the content (volume) of the plate-shaped filler to the total volume (volume) of the resin sheet is preferably 35 volume% or less, and may be, for example, 30 volume% or less, 25 volume% or less, or 20 volume% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than plate-shaped fillers, such as the connecting filler, are further enhanced. In one embodiment, the percentage may be, for example, 10-35 volume%, 15-35 volume%, 20-35 volume%, and 25-35 volume%, or 10-30 volume%, 15-30 volume%, 20-30 volume%, and 25-30 volume%, or 10-25 volume%, 15-25 volume%, and 20-25 volume%, or 10-20 volume%. However, these are just examples of the percentages.

[0040] <Connecting Filler> The aforementioned resin sheet has enhanced heat dissipation due to the inclusion of the connecting filler. The connecting filler is widely distributed in the resin sheet in both the planar and thickness directions, and as described later, the size of the connecting filler is small. Therefore, the connecting filler maintains contact with the plate-shaped filler in both the planar and thickness directions of the resin sheet, thereby connecting the plate-shaped fillers to each other through itself. As a result, the thermal conductivity of the resin sheet is increased in both the planar and thickness directions, and heat dissipation is enhanced. In particular, the resin sheet has increased thermal conductivity in the thickness direction due to the inclusion of the connecting filler, and thus heat dissipation is enhanced. If the resin sheet does not contain the connecting filler, the heat dissipation in the thickness direction of the resin sheet will not be enhanced in this way.

[0041] The average particle size of the connecting filler is 2 μm or less. This ensures that the plate-shaped fillers are sufficiently connected to each other by the connecting fillers. To further enhance this effect, the average particle size of the linked fillers 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 diameter of the linked filler is not particularly limited. For example, linked fillers with an average particle diameter of 0.5 μm or more are more readily available, and using such linked fillers makes it easier to improve the heat dissipation of the resin sheet. In one embodiment, the average particle size of the linked filler may be, for example, 0.5 to 2 μm, 0.5 to 1.5 μm, 0.5 to 1.2 μm, and 0.5 to 0.9 μm. However, these are just examples of the average particle size of the linked filler.

[0042] The shape of the connecting filler is not particularly limited, but it is preferably flat, and more preferably plate-shaped. Having a flat surface, and especially being plate-shaped, of the connecting filler increases the contact area between the connecting filler and the plate-shaped filler. As described above, since the surface direction of the plate-shaped filler tends to be the same as, or close to, the surface direction of the resin sheet, even if the connecting filler has a flat surface, the contact area between the connecting filler and the plate-shaped filler tends to decrease as the overall shape of the connecting filler deviates from plate-shaped. However, sufficient contact between the connecting filler and the plate-shaped filler is maintained by keeping the average particle diameter of the connecting filler at 2 μm or less.

[0043] The linking filler is preferably non-aggregated (not aggregated). The lower the content of aggregated linking filler in the resin sheet, the better the fluidity of the resin sheet when heated, and the higher its conformability to the object to which the resin sheet 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 connecting filler may be, for example, 5 W / m·K or higher, 10 W / m·K or higher, 25 W / m·K or higher, and 40 W / m·K or higher. There is no particular upper limit to the thermal conductivity of the connecting filler. For example, connecting fillers with a thermal conductivity of 400 W / m·K or less are more readily available. In one embodiment, the thermal conductivity of the connecting filler may be, for example, 5 to 400 W / m·K, 10 to 400 W / m·K, 25 to 400 W / m·K, and 40 to 400 W / m·K. However, these are just examples of the thermal conductivity of the connecting filler.

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

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

[0047] The connecting filler contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0048] The aforementioned linking filler is preferably made of magnesium hydroxide (Mg(OH)2) (i.e., a magnesium hydroxide filler). Since magnesium hydroxide is also a flame retardant, a resin sheet containing such a linking filler will have high heat dissipation and high flame retardancy.

[0049] The resin sheet containing magnesium hydroxide filler, or any other resin sheet that has been given flame retardancy, can, for example, meet UL94 standard grades V-0, V-1, or V-2.

[0050] In the resin sheet, the ratio of the content of the binding filler to the content of the plate-shaped filler ([Content of binding filler in the resin sheet (volume)] / [Content of plate-shaped filler in the resin sheet (volume)] × 100) is preferably 60 volume% or more, and may be, for example, 65 volume% or more, 70 volume% or more, 90 volume% or more, or 200 volume% or more. When the ratio is above the lower limit, the effect obtained by using the binding filler is further enhanced. In the resin sheet, the ratio of the content of the binding filler to the content of the plate-shaped filler is preferably 300 volume% or less, and may be, for example, 250 volume% or less, 140 volume% or less, 110 volume% or less, or 80 volume% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than binding fillers, such as the plate-shaped filler, are further enhanced. In one embodiment, the aforementioned ratio is preferably 60 to 300 volume%, and may be any of 65 to 300 volume%, 70 to 300 volume%, 90 to 300 volume%, and 200 to 300 volume%, or any of 60 to 250 volume%, 65 to 250 volume%, 70 to 250 volume%, and 90 to 250 volume%, or any of 60 to 140 volume%, 65 to 140 volume%, 70 to 140 volume%, and 90 to 140 volume%, or any of 60 to 110 volume%, 65 to 110 volume%, 70 to 110 volume%, and 90 to 110 volume%, or any of 60 to 80 volume%, 65 to 80 volume%, and 70 to 80 volume%. However, these are just examples of the aforementioned ratios.

[0051] In the resin sheet, the ratio of the content of the connecting filler (in volume parts) to the total volume (in volume parts) of the resin sheet ([Content of the connecting filler (in volume parts) of the resin sheet] / [Total volume (in volume parts) of the resin sheet] × 100) is preferably within the range of the ratio of the content of the connecting filler to the content of the plate-like filler described above. For example, it is preferably 6 volume% or more, and may be any of 9.8 volume% or more, 14 volume% or more, 20 volume% or more, and 25 volume% or more. When the ratio is above the lower limit, the effect obtained by using the connecting filler is further enhanced. In the resin sheet, the ratio of the content (volume) of the connecting filler to the total volume (volume) of the resin sheet is preferably 49 volume% or less, and may be, for example, 33 volume% or less, or 21 volume% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than the connecting filler, such as the plate-shaped filler, are further enhanced. In one embodiment, the percentage may be, for example, 6-49% by volume, 9.8-49% by volume, 14-49% by volume, 20-49% by volume, and 25-49% by volume; or 6-33% by volume, 9.8-33% by volume, 14-33% by volume, and 20-33% by volume; or 6-21% by volume, 9.8-21% by volume, and 14-21% by volume. However, these are just examples of the percentages.

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

[0053] The other components contained in the resin sheet may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0054] Examples of the other components mentioned above include additives known in the field. Examples of the aforementioned additives include antioxidants, antistatic agents, viscosity reducers, viscosity 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-shaped filler, and the connecting filler to the total mass (parts by mass) of the resin sheet (([Content of thermoplastic resin in the resin sheet (parts by mass)] + [Content of plate-shaped filler in the resin sheet (parts by mass)] + [Content of connecting filler in the resin sheet (parts by mass)]) / [Total mass (parts by mass) of the resin sheet] × 100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, 95% by mass or more, 97% by mass or more, or 99% by mass or more. When the ratio is above the lower limit, the heat dissipation and flexibility when heated of the resin sheet are balanced and further enhanced. On the other hand, the ratio is 100% by mass or less. The aforementioned ratio is typically the same as the ratio of the total content (parts by mass) of the thermoplastic resin, the plate-shaped filler, and the connecting filler to the total content (parts by mass) of components that do not vaporize at room temperature in the resin composition described later (([Content of thermoplastic resin in the resin composition (parts by mass)] + [Content of plate-shaped filler in the resin composition (parts by mass)] + [Content of connecting filler in the resin composition (parts by mass)]) / [Total content of components that do not vaporize at room temperature in the resin composition (parts by mass)] × 100).

[0056] The thickness of the resin sheet is preferably 100 μm or more, and may be, for example, 300 μm or more, 500 μm or more, 800 μm or more, or 1100 μm or more. A thickness of the resin sheet equal to or greater than the lower limit improves the heat dissipation performance of the resin sheet. On the other hand, the thickness of the resin sheet is preferably 2000 μm or less, and may be, for example, 1500 μm or less, or 1000 μm or less. When the thickness of the resin sheet is below the upper limit, the flexibility of the resin sheet when heated is increased. In one embodiment, the thickness of the resin sheet may be, for example, 100 to 2000 μm, 300 to 1500 μm, 500 to 1000 μm, and 800 to 1500 μm. However, these are just examples of resin sheet thicknesses. The thickness of the resin sheet is preferably adjusted according to the thickness of the object to which the resin sheet is applied, as will be described later.

[0057] <Characteristics of resin sheets> [Embedding rate R] When a test specimen consisting of one resin sheet with a thickness of T0, or a laminate of two or more resin sheets with a thickness of T0, is used, and a pressure of 12 kPa is applied to the test specimen in the thickness direction for 10 minutes in an environment of 100°C, and the thickness T1 of the test specimen at the pressure applied is measured, the following formula is obtained: R = (T0 - T1) / T0 × 100 The embedding ratio R calculated is 30% or more. The resin sheet of the first embodiment, in which the embedding ratio R is within this range, has high flexibility when heated. Therefore, the heating element can be well covered by the resin sheet. The method for calculating the embedment ratio R will be explained in more detail below, with reference to the drawings.

[0058] Figure 1 is a cross-sectional view illustrating a schematic method for calculating the embedding ratio R of the test specimen using the resin sheet. In addition, the diagrams used in the following explanation may be enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not be the same as in reality.

[0059] For example, to measure T1 (the thickness of the test specimen at the pressurized area after heating and pressurizing), as shown in Figure 1(a), the test specimen 10 is placed on a flat surface, and the indentation material 9 is placed near the center of one of the exposed surfaces 10a of the test specimen 10. The indentation material 9 is a means for pressing the test specimen 10 by contacting it and applying pressure. The test specimen 10 is either a single resin sheet itself or a laminate of two or more resin sheets. Regardless of which the test specimen 10 is, the thickness of the test specimen 10 in the thickness direction when no pressure is applied to the test specimen 10 is T0. T0 is not particularly limited and may be, for example, 500 μm or more, 1000 μm or more, and 1500 μm or more, or 3500 μm or less, 3000 μm or less, and 2500 μm or less.

[0060] In Figure 1, the indication of the contents of the test piece 10 (resin sheet) is omitted. In Figures 2 and onward, the indication of the contents of the resin sheet is also omitted in the cross-sectional view of the resin sheet in this embodiment.

[0061] The constituent material of the indentation material 9 is not particularly limited as long as it is hard, and examples include various ceramics. The shape of the indentation material 9 is not particularly limited as long as the contact surface with the test piece 10 is flat, and may be any of the following: prismatic, truncated pyramidal, cylindrical, truncated cone, elliptical prism, elliptical truncated pyramidal, etc. The area of ​​the contact surface (in other words, the pressing surface) 9b of the indentation material 9 with the test piece 10 should be smaller than the area of ​​one surface 10a of the test piece 10, but it is preferable that it be 0.05 to 0.30 times the area of ​​one surface 10a of the test piece 10.

[0062] Next, the weight 8 is placed on the other surface 9a of the indentation material 9 in this state (the upward-facing exposed surface that is not in contact with one surface 10a of the test piece 10). The weight 8 may be placed on a portion of the other surface 9a of the pressing material 9, or it may be placed on the entire surface. The weight 8 placed on the pressing 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, the indentation material 9, and the 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 the weight 8.

[0063] Next, the laminated material 100 in this state is immediately placed in an environment of 100°C and left to stand for 10 minutes. Based on the above, a pressure of 12 kPa is applied to the test specimen 10 in the thickness direction for 10 minutes under conditions of 100°C. When the laminate 100 is placed in an environment of 100°C, the heated test piece 10 softens and is pressed in by the indentation material 9, causing the contact area between the test piece 10 and the indentation material 9 to become indented. Next, immediately after 10 minutes have elapsed, the thickness T1 of the test specimen 10 at the pressure-applied portion of the heated and pressurized laminate 100 is measured.

[0064] As a result of the above, T0 and T1 can be measured, and using these measured values, the embedding rate R of the test piece 10 is calculated using the above formula.

[0065] In terms of easily covering the heating element with a 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, resin sheets with an embedding ratio R of 65% or less, or 60% or less, can be manufactured more easily. In one embodiment, the implantation rate R may be, for example, 30-65%, 35-65%, 40-65%, 45-65%, and 50-65%, or 30-60%, 35-60%, 40-60%, and 45-60%. However, these are just examples of implantation rates 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 higher, more preferably 3 W / m·K or higher, and may be, for example, 4 W / m·K or higher. The resin sheet having a thermal conductivity equal to or greater than the lower limit has high heat dissipation 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 manufactured more easily. 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, and 4 to 15 W / m·K. The thermal conductivity of a resin sheet in the planar direction, not limited to the aforementioned resin sheet, more specifically refers to the thermal conductivity of the resin sheet in a direction parallel to one or the other surface of the resin sheet.

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

[0069] The thermal conductivity of the resin sheet in the planar direction can be adjusted, for example, by adjusting the type of thermoplastic resin and its content in the resin sheet; the type of plate-shaped 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] [Relative permittivity] The relative permittivity 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. The resin sheet having a relative permittivity at a frequency of 10 GHz that is below the upper limit is particularly suitable for covering and mounting a heating element on a circuit board, for example, because it has high insulating properties and is highly effective in suppressing the generation of electrical signal noise in circuits within the object to which the resin sheet is attached. The lower limit of the relative permittivity at a frequency of 10 GHz is not particularly limited. For example, a resin sheet having a relative permittivity of 1 or more at a frequency of 10 GHz can be manufactured more easily. In one embodiment, the relative permittivity at a frequency of 10 GHz may be, for example, 1 to 4, 1 to 3.75, 1 to 3.65, and 1 to 3.55. However, these are just examples of the relative permittivity at a frequency of 10 GHz. The relative permittivity at a frequency of 10 GHz is preferably measured under normal temperature conditions (for example, under a temperature of 23°C).

[0071] The relative permittivity 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 and 3.8 or less. The resin sheet having a relative permittivity at a frequency of 1 GHz that is below the upper limit is particularly suitable for covering and mounting a heating element on a circuit board, for example, because it has high insulating properties and is highly effective in suppressing the generation of electrical signal noise in circuits within the object to which the resin sheet is attached. The lower limit of the relative permittivity at a frequency of 1 GHz is not particularly limited. For example, a resin sheet having a relative permittivity of 1 or more at a frequency of 1 GHz can be manufactured more easily. In one embodiment, the relative permittivity at a frequency of 1 GHz may be, for example, 1 to 4, 1 to 3.9, and 1 to 3.8. However, these are just examples of the relative permittivity at a frequency of 1 GHz. The relative permittivity at a frequency of 1 GHz is preferably measured under normal temperature conditions (for example, under a temperature of 23°C).

[0072] The relative permittivity of the resin sheet can be adjusted regardless of frequency by adjusting the type and amount of components contained in the resin sheet.

[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. A resin sheet having a dielectric loss tangent in this range at a frequency of 10 GHz has high radio wave transparency and is suitable for constructing electronic equipment equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 10 GHz is not particularly limited. For example, a resin sheet having a dielectric loss tangent of 0.001 or higher at a frequency of 10 GHz can be manufactured more easily. 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, and 0.001 to 0.0045. However, these are just examples of the dielectric loss tangent at a frequency of 10 GHz. The dielectric loss tangent at a frequency of 10 GHz is preferably measured under normal temperature conditions (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 and 0.008 or less. A resin sheet having a dielectric loss tangent in this range at a frequency of 1 GHz has high radio wave transparency and is suitable for constructing electronic equipment equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 1 GHz is not particularly limited. For example, a resin sheet having a dielectric loss tangent of 0.001 or more at a frequency of 1 GHz can be manufactured more easily. 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, and 0.001 to 0.008. However, these are just 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 under normal temperature conditions (for example, at a temperature of 23°C).

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

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

[0077] [density] The density of the aforementioned resin sheet is 2 g / cm³. 3 Preferably, the following, for example, 1.7 g / cm³ 3 The following is also possible. Various electronic devices constructed by attaching such resin sheets are suitable for use in constructing portable electronic devices, for example, because they suppress heat generation and are lightweight. The lower limit of the density of the resin sheet is not particularly limited. For example, if the density is 1 g / cm³ 3 The aforementioned resin sheet can be realized more easily. In one embodiment, the density of the resin sheet is, for example, 1 to 2 g / cm³. 3 , and 1-1.7 g / cm³ 3 Any of the above may be used. 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 amounts of 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 pipe method).

[0079] The resin sheet may be irradiated with an electron beam. In that case, it is preferable that the resin sheet is irradiated with an electron beam under conditions of an absorbed dose of 20 to 300 kGy. The acceleration voltage for electron beam irradiation is preferably 100 to 300 kV. By irradiating the aforementioned resin sheet with an electron beam, the resin sheet is partially crosslinked, improving its heat resistance and repairability.

[0080] <<Resin composition and method for producing the same>> A resin sheet according to the first embodiment can be manufactured, for example, by using a resin composition (which may be referred to as the "resin composition according to the first embodiment" in this specification) comprising the thermoplastic resin, the plate-shaped filler, the connecting filler, and, if necessary, the other components.

[0081] The resin composition may also contain a solvent in addition to the components described above. The resin composition containing a solvent may have improved handling properties. In this specification, unless otherwise specified, the term "solvent" refers not only to components capable of dissolving solutes in solution, but also to components that act as a dispersion medium in a dispersion.

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

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

[0085] The resin composition can be produced by blending the thermoplastic resin, the plate-shaped filler, the connecting filler, the other components as needed, and the solvent as needed. There are no particular restrictions on the order in which each component is added during formulation, and two or more components may be added simultaneously. The method of mixing each component during formulation is not particularly limited and can be appropriately selected from known methods. The temperature and time during the addition and mixing of each component are not particularly limited, as long as the individual components do not deteriorate, and can be adjusted as appropriate.

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

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

[0088] The molding temperature (pressure temperature) of the resin composition is preferably higher than the melting point of the thermoplastic resin. For example, it may be 15°C or more higher than the melting point of the thermoplastic resin, 35°C or more higher than the melting point of the thermoplastic resin, or 55°C or more higher than the melting point of the thermoplastic resin. By setting the molding temperature 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 applied during molding of the resin composition is not particularly limited, as long as the effect of pressurization is sufficiently obtained, but it is preferably 3 MPa or higher, and may be, for example, 8 MPa or higher, or 13 MPa or higher. A pressure above the lower limit allows for the acquisition of a more uniform resin sheet. The upper limit of the aforementioned 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 time) of the resin composition is not particularly limited as long as the effect of pressurization is sufficiently obtained, and can be set arbitrarily according to the pressure during molding as described above, but it is preferably 0.5 minutes or more. By setting the molding time to be 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 such as a pressure of 0.05 MPa or less. By molding under reduced pressure in this way, a resin sheet with higher uniformity can be obtained.

[0092] <<Resin sheet (second embodiment)>> A resin sheet according to a second embodiment of one embodiment of the present invention comprises a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle diameter of the connecting filler is 2 μm or less. The resin sheet of the second embodiment, because it contains the plate-shaped filler and the connecting filler, has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and in the thickness direction. Furthermore, because the resin sheet of the second embodiment contains a thermoplastic resin, it has flexibility when heated. The resin sheet of the second embodiment may be the same as the resin sheet of the first embodiment, except that the embedding ratio R described above is not specified to be 30% or more. By covering, and preferably embedding, a heat-generating element such as a CPU with a resin sheet of the second embodiment having such characteristics, a new heat dissipation structure can be constructed in various electronic devices, and a high effect in suppressing heat generation can be obtained in various electronic devices. Furthermore, the heat dissipation structure can be constructed not only for CPUs but also for other devices equipped with heat-generating elements similar to those of a CPU, and a high effect in suppressing heat generation can be obtained.

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

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

[0095] The thermoplastic resin, plate-shaped filler, and connecting filler included in the resin sheet of the second embodiment are the same as those included in the resin sheet of the first embodiment described above. The components contained in the resin sheet of the second embodiment produce the same effects in the resin sheet of the second embodiment as in the resin sheet of the first embodiment.

[0096] The embodiment of the second embodiment in which the resin sheet comprises a thermoplastic resin, a plate-shaped filler, a connecting filler, and the other components may be the same as the embodiment of the first embodiment in which the resin sheet comprises a thermoplastic resin, a plate-shaped filler, a connecting filler, and the other components. More specifically, for example, the following:

[0097] The thermoplastic resin, plate-shaped filler, connecting filler, and other components contained in the resin sheet of the second embodiment may each be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to 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 embodiment, the ratio of the thermoplastic resin content (parts by mass) to the total mass (parts by mass) of the resin sheet ([thermoplastic resin content (parts by mass) of the resin sheet] / [total mass (parts by mass) of the resin sheet] × 100) is preferably 20% by mass or more and preferably 45% by mass or less, for the same reasons as in the case of the resin sheet of the first embodiment. For example, it may be 20 to 45% by mass, and may be within the same numerical range as in the case of the resin sheet of the first embodiment.

[0100] The plate-shaped filler included in the resin sheet of the second embodiment is preferably made of boron nitride (BN) or aluminum oxide (Al2O3) (i.e., boron nitride filler or aluminum oxide filler), and more preferably made of boron nitride (i.e., boron nitride filler), for the same reasons as in the case of the resin sheet of the first embodiment.

[0101] The average particle size of the plate-shaped 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, but may also be 15 μm or less, for example, 5 to 15 μm, and may be within 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) of plate-shaped filler to the total volume (volume) of the resin sheet ([content (volume) of plate-shaped filler in the resin sheet] / [total volume (volume) of the resin sheet] × 100) is preferably 10 vol% or more and preferably 35 vol% or less, for the same reasons as in the resin sheet of the first embodiment. For example, it may be between 10 and 35 vol%, and may be within the same numerical range as in the resin sheet of the first embodiment.

[0103] The connecting filler included in the resin sheet of the second embodiment is preferably made of magnesium hydroxide (Mg(OH)2) (i.e., a magnesium hydroxide filler) for the same reasons as in the case of the resin sheet of the first embodiment. The second embodiment of the flame-retardant resin sheet, such as the resin sheet containing magnesium hydroxide filler, can, for example, satisfy UL94 standard grades V-0, V-1, or V-2.

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

[0105] In the resin sheet of the second embodiment, the ratio of the content of the connecting filler (in volume parts) to the total volume (in volume parts) of the resin sheet ([Content of the connecting filler (in volume parts) of the resin sheet] / [Total volume (in volume parts) of the resin sheet] × 100) is preferably within the numerical range that satisfies the ratio of the content of the connecting filler to the content of the plate-like filler described above. For the same reasons as in the case of the resin sheet of the first embodiment, it is preferably 6 vol% or more and preferably 49 vol% or less, for example, it may be 6 to 49 vol%, and may be within 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 thermoplastic resin, plate-shaped filler, and connecting filler to the total mass (parts by mass) of the resin sheet (([Content of thermoplastic resin in the resin sheet (parts by mass)] + [Content of plate-shaped filler in the resin sheet (parts by mass)] + [Content of connecting filler in the resin sheet (parts by mass)]) / [Total mass (parts by mass) of the resin sheet] × 100) is preferably 80% by mass or more and 100% by mass or less, for the same reasons as in the case of the resin sheet of the first embodiment.

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

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

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

[0110] The relative permittivity of the resin sheet of the second embodiment, measured in accordance with the TM0m0 mode cavity resonator perturbation method at a frequency of 1 GHz, is preferably 4 or less for the same reasons as in the case of the resin sheet of the first embodiment, but may also be 1 or more, for example, 1 to 4, and may be within the same numerical range as in the case of the resin sheet of the first embodiment. In the second embodiment, the relative permittivity at a frequency of 1 GHz is preferably a measurement taken 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, but may also be 0.001 or more, for example, 0.001 to 0.01, and may be within 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 measured under normal temperature conditions (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, but may also be 0.001 or more, for example, 0.001 to 0.01, and may be within the same numerical range as the resin sheet of the first embodiment. In the second embodiment, the dielectric loss tangent at a frequency of 1 GHz is preferably a measurement taken 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 permittivity at a frequency of 10 GHz and the relative permittivity at a frequency of 1 GHz are both within the above numerical range. In the resin sheet of the second embodiment, it is preferable that the dielectric loss tangent at a frequency of 10 GHz and the dielectric loss tangent at a frequency of 1 GHz are both within the above numerical range. In the resin sheet of the second embodiment, it is more preferable that the relative permittivity at a frequency of 10 GHz, the relative permittivity at a frequency of 1 GHz, the dielectric loss tangent at a frequency of 10 GHz, and the dielectric loss tangent at a frequency of 1 GHz are all within the above numerical range.

[0114] The density of the resin sheet in the second embodiment is 2 g / cm³ for the same reasons as in the case of the resin sheet in the first embodiment. 3 Preferably, it is 1 g / cm³ 3 It may be greater than or equal to 1-2 g / cm³. 3 This may be the case, and the numerical range may be the same 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, for example, in the same manner as in the case of the resin sheet of the first embodiment, and can be measured in the same manner as in the case of the resin sheet of the first embodiment.

[0116] The resin sheet of the second embodiment allows for easier adjustment of its flexibility during heating, 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. By adjusting the type and content of the components contained in the resin sheet of the second embodiment in this way, the resin sheet of the second embodiment can be given the same flexibility during heating as the resin sheet of the first embodiment, in which the embedding 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, preferably irradiated with an absorbed dose of 20 to 300 kGy, and the acceleration voltage for electron beam irradiation is preferably 100 to 300 kV.

[0118] The resin sheet of the second embodiment can be manufactured, for example, by using a resin composition (which may be referred to as the "resin composition of the second embodiment" in this specification) comprising the thermoplastic resin, the plate-shaped filler, the connecting filler, and, if necessary, the other components. The resin composition of the second embodiment is the same as the resin composition for manufacturing the resin sheet of the first embodiment described above (the resin composition of the first embodiment), except that the type and / or amount of the constituent components may differ. For example, the resin composition of the second embodiment may contain a solvent, and the solvent may be the same as the solvent that may be contained in the resin composition of the first embodiment.

[0119] The resin composition of the second embodiment can be manufactured in the same manner as the resin composition of the first embodiment, except that the type and / or amount of the constituent components may differ.

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

[0121] <<Method of using the resin sheet of the first embodiment and the resin sheet of the second embodiment>> By using the aforementioned resin sheets (the resin sheet of the first embodiment and the resin sheet of the second embodiment) to cover the surface of a heat-generating element such as a CPU, a new heat dissipation structure can be constructed in various electronic devices, thereby suppressing heat generation in various electronic devices.

[0122] <How to use 1> Figure 2 is a schematic cross-sectional view illustrating an example of how to use the resin sheet (which may be referred to as "Method 1 of Use" in this specification). Here, an example is shown in which the entire exposed surface of the heating element is covered with the resin sheet, that is, in which the heating element is embedded.

[0123] In the figures after FIG. 2, the same components as those shown in the already described figures are denoted by the same reference numerals as in the case of the already described figures, and the detailed description thereof is omitted.

[0124] In Usage Method 1, first, as shown in FIG. 2(a), a laminated structure 101 is prepared in which a resin sheet 1, a heat spreader 4, and a housing 3 are laminated in this order in their thickness directions. The resin sheet 1 is the resin sheet of the above-described present embodiment (the resin sheet of the first aspect or the resin sheet of the second aspect). The housing 3 is a known one and can be arbitrarily selected according to the purpose. Examples of the constituent material of the housing 3 include resin, metal, carbon material, and the like. The heat spreader 4 is also a known one, and examples of its constituent material include metals such as copper; carbon materials such as graphite, and the like.

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

[0126] The thickness T of the resin sheet 1 x is preferably within the numerical range described above. On the other hand, the thickness T of the resin sheet 1 x is preferably 0.5 to 1.5 times, more preferably 0.6 to 1.3 times, and may be, for example, 0.6 to 1 times, the height (thickness) of the object to which it is applied. When T x is equal to or greater than the lower limit value, the object to which the resin sheet 1 is applied can be more easily covered. When T x is equal to or less than the upper limit value, it is possible to avoid the resin sheet 1 having an excessive thickness. Since the resin sheet 1 has high flexibility during heating, when the resin sheet 1 is pressed against the object to which it is applied, a region pushed aside by the object to which it is applied occurs in the resin sheet 1, and this region can contribute to maintaining the thickness of the resin sheet 1. Therefore, T xHowever, even if the resin sheet 1 is less than or equal to the height (thickness) of the object to be applied, the object can be sufficiently embedded in the resin sheet 1. Thickness T of resin sheet 1 x It is preferable that the numerical range described above is satisfied, as well as the numerical range based on the height of the object to which it is applied. If the height (thickness) of the object to be applied is not constant, the height (thickness) of the highest point (thickest point) shall be used 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 part 6 when the resin sheet 1 covers the entire exposed surface of the heating element 5 and the entire exposed portion of the connecting part 6, and its height is indicated by the symbol T in Figure 2(a). y This is indicated by the notation. In contrast, for example, if the resin sheet 1 covers the entire exposed surface of the heating element 5 but does not cover the connecting 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 part 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 corresponding to this exposed surface.

[0128] The laminated structure 101 is positioned near 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). That is, one surface 1a of the resin sheet 1 faces the exposed surface 5a of the heating element 5.

[0129] In Method 1, the laminated structure 101 is then moved in the direction of arrow P1 to press the resin sheet 1 against the heating element 5, or the heating element 5 on the circuit board 7 is moved together with the circuit board 7 in the direction of arrow P2 to press the heating element 5 against the resin sheet 1, or the laminated structure 101 is moved in the direction of arrow P1 and the heating element 5 on the circuit board 7 is moved together with the circuit board 7 in the direction of arrow P2 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 Figure 2(b). At this time, a portion 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 is facing the resin sheet 1, and further, another portion of one surface 1a of the resin sheet 1 is brought into contact with one surface 7a of the circuit board 7, or brought close to the vicinity of one surface 7a of the circuit board 7. This allows the resin sheet 1 to cover the entire exposed surface 5a of the heating element 5 (including the top and sides), thereby embedding the heating element 5.

[0130] Figure 2(b) shows a state in which one heating element 5 is provided on one side 7a of the circuit board 7. However, there may be only one heating element on one side 7a of the circuit board 7, or there may be two or more. If there are two or more heating elements on one side 7a of the circuit board 7, these two or more heating elements may be identical or different. That is, the two or more heating elements may all be identical, all be different, or only partially identical.

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

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

[0133] When covering the heating element 5 with the resin sheet 1 (embedding the heating element 5 in Figure 2), it is preferable to adjust the temperature of the heating element 5 to a temperature similar to the molding temperature (pressure temperature) of the resin composition described earlier (a temperature based on the melting point of the thermoplastic resin). By adjusting the temperature of the heating element 5 in this way, the heating element 5 can be covered more uniformly with the resin sheet 1, the heat dissipation performance of the resin sheet 1 is improved, and the heat dissipation efficiency of the heating element 5 is improved. The temperature of the heating element 5 can be adjusted using known temperature control means such as an oven.

[0134] When covering the heating element 5 with the resin sheet 1 (embedding it in Figure 2), the pressure applied to the resin sheet 1 when pressing the resin sheet 1 against the heating element 5, and the pressure applied to the heating element 5 (more specifically, the circuit board 7) when pressing the heating element 5 against the resin sheet 1, are preferably 10 to 20 kPa. A pressure of 10 to 20 kPa or higher allows the resin sheet 1 to cover the heating element 5 more uniformly. A pressure of 10 to 20 kPa or lower avoids excessive pressure. Because the resin sheet 1 is highly flexible when heated, it can adequately cover the heating element 5 even at a low pressure of around 10 to 20 kPa.

[0135] In this state, with the heating element 5 covered by the resin sheet 1, the high flexibility of the resin sheet 1 during heating results 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 connecting 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 connecting portion 6. By adjusting the conditions when covering the heating element 5 with the resin sheet 1, it is possible to eliminate the existence of such gaps (completely prevent the occurrence of such gaps).

[0136] In this state, with the heating element 5 covered by the resin sheet 1, the heat generated by the heating element 5 is transferred within the resin sheet 1 in the planar direction D S The heat is conducted along the surface and, for example, dissipated into the atmosphere. Furthermore, the heat generated by the heating element 5 is released in the resin sheet 1 in the thickness direction D T The heat is conducted along the thickness direction D and dissipated into the atmosphere via the heat spreader 4. At this time, because the heating element 5 is embedded in the resin sheet 1, the distance between the heating element 5 and the heat spreader 4 is shorter than if it were not embedded, and in the thickness direction D T The heat dissipation in the thickness direction D of the resin sheet 1 is improved. T The heat conducted along the surface may also be dissipated into the atmosphere via the circuit board 7. If the housing 3 is made of a highly thermally conductive material such as metal or carbon material, the thickness direction D of the resin sheet 1 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 casing 3. If the housing 3 is made of a highly thermally conductive material such as metal or carbon material, the heat spreader 4 may be omitted in the laminated structure 101.

[0137] As described above, the resin sheet 1 has high thermal conductivity and high heat dissipation in both its planar and thickness directions, and furthermore, it has high flexibility when heated. The heat dissipation structure using such a resin sheet 1 in Method of Use 1 is something that has not been seen at all in conventional heat dissipation structures.

[0138] <How to use 2> Figure 3 is a schematic cross-sectional view illustrating another example of how to use the resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment) (which may be referred to as "Method of Use 2" in this specification). Here, an example is shown in which only a portion of the exposed surface of the heating element is covered with the resin sheet, that is, in which the heating element is not embedded.

[0139] The laminated structure 101 prepared in Method 2 is the same as the laminated structure 101 prepared in Method 1, as shown in Figure 3(a). In Method 2, the target object for application of the resin sheet 1 is the heating element 5, and more specifically, the area of ​​the heating element 5 corresponding to a part of the exposed surface 5a, with a height T y This differs from the case of Method 1.

[0140] In Method 2, the heating element 5 is then covered with the resin sheet 1 in the same manner as in Method 1, as shown in Figure 3(b). However, in this case, one side 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 is not extended in the thickness direction of the resin sheet 1 to a position that coincides with the contact area between the heating element 5 and the connection part 6, so that a portion of the lower (side) 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 when the heating element 5 is covered with the resin sheet 1 in this manner, 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, similar to the case of Method 1 of Use. More specifically, the formation of gaps is suppressed between one surface 1a of the resin sheet 1 and the region of the exposed surface 5a of the heating element 5 that the resin sheet 1 reaches in the thickness direction of the resin sheet 1. By adjusting the conditions when the heating element 5 is covered with the resin sheet 1, it is possible to eliminate the existence of such gaps (completely prevent the formation of such gaps).

[0142] As described above, except that the object to which the resin sheet 1 is applied is different (for example, covering only a portion of the exposed surface 5a of the heating element 5 with the resin sheet 1 instead of the entire area), method of use 2 is the same as method of use 1, and the effect achieved by method of use 2 is the same as the effect achieved by method of use 1.

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

[0144] For example, when covering a heating element with a resin sheet, if the region of one side of the resin sheet (the side facing the circuit board, for example, one side 1a of resin sheet 1 in Figures 2 and 3) that is closest to the circuit board does not come into contact with one side of the circuit board (the side facing the resin sheet, for example, one side 7a of circuit board 7 in Figures 2 and 3), then the resin sheet may be positioned in the thickness direction of the resin sheet at a location that coincides with the contact area between the heating element 5 and the connection part 6.

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

[0146] As described above, the resin sheet of this embodiment has high flexibility when heated, making it excellent for covering and preferably embedding heating elements. Therefore, the heat dissipation properties of the resin sheet of this embodiment are extremely good. In contrast, conventional heat-dissipating sheets, such as graphite sheets, have excellent heat dissipation properties, but they lack conformability to the object being cooled and their adhesion to the object is insufficient. Therefore, they are unsuitable as a heat dissipation structure to be installed on a heat-generating element on their own. Furthermore, heat-dissipating sheets such as graphite sheets are also conductive sheets, and due to their conductivity (they do not have insulating properties), they cannot be used in areas near antennas. For example, thermal interface materials (TIMs) have good adhesion to the object being cooled and also possess insulating properties, but their heat dissipation and conformability to the object being cooled are insufficient. For example, while liquid heat dissipation materials are known to exist at room temperature, their use is limited to enclosed spaces, their filling process is complicated, and their repairability is poor. The resin sheet of this embodiment can solve all of these conventional problems. [Examples]

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

[0148] [Thermoplastic resin] Thermoplastic resin (a1): Ethylene-vinyl acetate copolymer (EVA) ("EVAflex® EV150" manufactured by Mitsui Dow Polychemicals, melting point approximately 60°C, MFR 30g / 10min, density 0.96g / cm³) 3 , vinyl acetate content 33% by mass) The MFR of the aforementioned EVA was measured in accordance with JIS K7210:1999, under a temperature of 190°C and with a load of 2.16 kg applied.

[0149] [Sheet-shaped filler] Plate-shaped filler (b1): Plate-shaped boron nitride filler (Tokuyama Corporation "K03", average particle size 9 μm, density 2.3 g / cm³) 3 (Thermal conductivity 60 W / m·K, aspect ratio 30, relative permittivity 4) [Connecting filler] Linked filler (c1): Magnesium hydroxide filler surface-treated with higher fatty acids (Kyowa Chemical Industry Co., Ltd.'s "KISUMA® 5B," 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) (Kyowa Chemical Industry Co., Ltd.'s "KISUMA® 5P", 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) (Kyowa Chemical Industry Co., Ltd. "KISUMA® 5L", 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 (Kyowa Chemical Industry Co., Ltd. "KISUMA (registered trademark) 5", average particle size 0.83 μm, thermal conductivity 8 W / m·K) Linked filler (c5): Magnesium hydroxide filler (Kyowa Chemical Industry Co., Ltd. "KISUMA® 8", average particle size 1.38 μm, thermal conductivity 8 W / m·K) [Other fillers] Other fillers (d1): Cardhouse-type aluminum oxide filler (DIC Corporation "AC75", average particle size 70 μm, density 3.97 g / cm³) 3 (Thermal conductivity 20 W / m·K) Other fillers (d2): Polyhedral aluminum oxide filler (DIC Corporation "AH40-S", average particle size 32 μm, density 3.97 g / cm³) 3 (Thermal conductivity 20 W / m·K)

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

[0151] <<Evaluation of resin sheets>> <Calculation of embedding ratio R> Three resin sheets (700 μm thick) obtained by the above method were laminated in their respective thickness directions and cut to a size of 3.5 cm × 3.5 cm to produce a test specimen with a thickness T0 of 2100 μm and a rectangular planar shape. Next, the obtained test specimen was placed on a flat surface, and a cylindrical ceramic indentation material, 16 mm in diameter and 14 mm in height, was placed near the center of the upward-facing exposed surface of the test specimen. At this time, one flat surface of the indentation material, rather than the curved surface, was in contact with the exposed surface of the test specimen. Furthermore, a weight was placed over the entire surface of the other flat surface of the indentation material (the upward-facing exposed surface that was not in contact with the exposed surface of the test specimen). By stacking the test specimen, indentation material, and weight in this order, a pressure of 12 kPa was applied to the test specimen in the thickness direction. This stack was then immediately moved to a 100°C environment and left to stand for 10 minutes. As a result, a pressure of 12 kPa in the thickness direction of the test specimen was applied to the test specimen for 10 minutes at 100°C. Next, after 10 minutes had elapsed, the thickness T1 of the test specimen at the pressure-applied portion of the laminate in this state was immediately measured. Then, the embedding ratio R of the test specimen (resin sheet) was calculated using the formula described above. The results are shown in Table 1.

[0152] <Confirmation of heat dissipation properties of resin sheets (1)> The resin sheet (700 μm thick) obtained above was cut into 10 cm x 10 cm pieces.

[0153] Four resistors were arranged in a row on the circuit side of a circuit board at approximately equal intervals. These four resistors were numbered (1-1) to (1-4) from one end of the row to the other. Furthermore, in a direction perpendicular to the direction of this row, one additional resistor was placed on the same side as these four resistors (i.e., resistors (1-1), (1-2), (1-3), and (1-4)), at approximately equal distances from each of the four resistors. These four separately placed resistors were numbered (2-1) to (2-4) from one end of the row to the other. Resistor (2-1) is adjacent to resistor (1-1) and not to resistor (1-4); resistor (2-2) is adjacent to resistor (1-2) and not to resistor (1-3); resistor (2-3) is adjacent to resistor (1-3) and not to resistor (1-2); and resistor (2-4) is adjacent to resistor (1-4) and not to resistor (1-1). As a result, eight resistors in total are placed on the circuit surface of the circuit board, with four resistors per row for two rows, and the spacing between adjacent resistors in two orthogonal directions is approximately equal. The height of these eight resistors (i.e., the distance between the top surface of the resistor (the side opposite to the circuit board) and the circuit surface of the circuit board) was approximately 4 mm. A schematic plan view showing the placement of the resistors on the circuit board at this time is shown in Figure 4.

[0154] Next, one thin-wire thermocouple was placed on each of the two resistors at the ends of the four resistors in one row (resistor (1-1) and resistor (1-4)). Furthermore, one thin-wire thermocouple was placed on the second resistor from one end of the four resistors in the other row (resistor (2-2)). Then, one thin-wire thermocouple was placed in a part of the circuit board's circuit surface that was midway between these two rows and approximately in the center in the direction of the two rows (approximately the center of the circuit board's circuit surface), where no resistors were placed. In other words, one thermocouple was placed on each of the three of the eight resistors on the circuit surface, and one thermocouple was placed on the circuit surface rather than on a resistor. The placement positions of the thermocouples at this time are shown in Figure 4.

[0155] Next, for all eight resistors on the circuit board, a sheet of thermal interface material (TIM, Widework's "Thermo-TranzH2", 500 μm thick) was laminated over the entire surface of the side of each resistor opposite to the circuit board. This was done to prevent variations in the height of the eight resistors from affecting the evaluation results, as their heights are not exactly the same. As a result, the thermocouples on the resistors were positioned between the resistor and the thermal interface material (TIM) sheet. Furthermore, the entire surface of the side of these thermal interface material sheets opposite to the resistors was covered with the aforementioned single resin sheet (700 μm thick). Finally, a polycarbonate substrate (2000 μm thick) was placed over the entire surface of the resin sheet opposite to the thermal interface material sheet. Thus, a test circuit board was fabricated to evaluate the heat dissipation performance of the resin sheet.

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

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

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

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

[0160] <<Manufacturing and evaluation of resin sheets>> [Comparative Example 1] A pelletized resin composition was prepared by melt-kneading thermoplastic resin (a1) (500g), other filler (d1) (1000g), connecting filler (c4) (300g), and connecting filler (c5) (300g) using a twin-screw extruder. Then, a resin sheet (700 μm thick) was manufactured and evaluated using the same method as in Example 1, except that this pelletized resin composition was used. The results are shown in Table 1 and Figure 6. Figure 6 is image data obtained when the heat dissipation performance of the resin sheet was confirmed in this comparative example.

[0161] [Comparative Example 2] A pelletized resin composition was prepared by melt-kneading thermoplastic resin (a1) (500g), other filler (d2) (1000g), connecting filler (c4) (300g), and connecting filler (c5) (300g) using a twin-screw extruder. Then, a resin sheet (700 μm thick) was manufactured and evaluated using the same method as in Example 1, except that this pelletized resin composition was used. The results are shown in Table 1 and Figure 7. Figure 7 is image data obtained when the heat dissipation performance of the resin sheet was confirmed in this comparative example.

[0162] <<Evaluation of test resin sheets>> <Confirmation of heat dissipation properties of test resin sheets> [Test Example 1] As a test resin sheet, a commercially available thermally conductive sheet (thickness 500 μm) whose main component is rubber and whose thermal conductivity in the planar direction is 3 W / m·K was prepared. In the same manner as in Example 1, "Confirmation of the heat dissipation performance of the resin sheet," eight resistors and four thermocouples were placed on the circuit surface of the circuit board. Next, for all eight resistors on the circuit board, a sheet of thermal interface material (TIM, Widework's "Thermo-TranzH2", 500 μm thick) was laminated to the entire surface of the side of the resistor opposite to the circuit board, via a thermocouple if one was placed there. This positioned the thermocouple on the resistor between the resistor and the thermal interface material (TIM) sheet. Furthermore, the entire surface of the side of these thermal interface material sheets opposite to the resistor was covered with the aforementioned single test resin sheet (500 μm thick). Finally, a polycarbonate substrate (2000 μm thick) was placed on the entire surface of the test resin sheet opposite to the thermal interface material sheet after this covering. Thus, a test circuit board was fabricated to evaluate the heat dissipation performance of the test resin sheet. In the following, using the same method as in Example 1, a voltage was applied to the test circuit board, and the surface temperature of the polycarbonate substrate was measured using a thermograph. The image data obtained at this time is shown in Figure 8. Furthermore, the temperatures detected by thermocouples on the resistor and circuit surface are shown in Table 1.

[0163] In Table 1, "Sheet-shaped filler content (volume %)" refers to the ratio of the sheet-shaped filler content (volume parts) to the total volume (volume parts) of the resin sheet. Similarly, "bonding filler content (volume %)" refers to the ratio of the bonding filler content (volume parts) to the total volume (volume parts) of the resin sheet. "The ratio of the content of linked fillers to the content of plate-shaped fillers (volume %)" refers to the ratio of the content of linked fillers (volume portion) to the content of plate-shaped fillers (volume portion) in a resin sheet. These principles also apply to the tables following Table 1.

[0164] [Table 1]

[0165] As is clear from the results above, in Example 1, the embedding rate R was high at 43.8%, and the flexibility of the resin sheet when heated was high. As shown in Figure 5, the surface of the polycarbonate substrate was heated to approximately 65-85°C in the region where four resistors in the same row were located, spanning across these resistors, and this was similar in the region where two rows were located. Furthermore, the region between these two rows was also heated to approximately 60-65°C. This indicates that the heat generated from the four resistors in the same row was dissipated not only in the length direction of the row but also in the width direction of the row by the resin sheet, demonstrating that the resin sheet has high heat dissipation properties in its planar direction. On the other hand, as shown in Table 1, when comparing the thermocouple detection temperatures between identical resistors and between circuit surfaces of the circuit board in Example 1 and Test Example 1, the detection temperature in Example 1 was lower than that in Test Example 1. This indicates that the resin sheet in Example 1 has higher heat dissipation properties not only in its planar direction but also in its thickness direction than the test resin sheet (commercially available thermally conductive sheet) in Test Example 1. In the above evaluation, the heat dissipation performance of the resin sheet relative to the heating element (resistor) was simply confirmed without embedding the heating element in the resin sheet. However, it was inferred that the resin sheet of Example 1 would also exhibit high heat dissipation performance when the heating element is covered over a wider area, and preferably embedded. Thus, it was confirmed that the resin sheet of Example 1 has high flexibility when heated, high heat dissipation performance in both the planar and thickness directions, and can be used to construct a new heat dissipation structure. The resin sheet of Example 1 contained a thermoplastic resin, a plate-shaped filler, and a connecting filler. In the sheet of Example 1, the ratio of the connecting filler content to the plate-shaped filler content was 72.0% by volume.

[0166] The dielectric constant of the resin sheet in Example 1 satisfied the condition of being less than 4 in both cases of frequencies 1 GHz and 10 GHz. The dielectric loss tangent of the resin sheet in Example 1 satisfied the condition of being 0.01 or less in both the 1 GHz and 10 GHz cases. The density of the resin sheet in Example 1 is 2 g / cm³. 3 The following conditions were met:

[0167] In contrast, in Comparative Example 1, the embedding rate R was low at 11.0%, the flexibility of the resin sheet when heated was low, and the resin sheet could not cover a wider area of ​​the heating element, or more preferably, embed it. Furthermore, as shown in Figure 6, the surface of the polycarbonate substrate was heated to approximately 65-85°C in the region where four resistors in the same row were located, spanning these resistors. This was similar in the region where two rows were located, but the heated region was narrower than in Example 1. The region between these two rows was not heated to a high temperature. This indicates that although the heat generated from the four resistors in the same row was dissipated by the resin sheet in the longitudinal 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 planar 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 comparing the thermocouple detection temperatures for the same resistors in Comparative Example 1 and Test Example 1, the detection temperatures were higher in Comparative Example 1 than in Test Example 1 in all cases, indicating that the resin sheet of Comparative Example 1 had lower heat dissipation than the test resin sheet (commercially available thermally conductive sheet) used in Test Example 1. Thus, the resin sheet of Comparative Example 1 had low flexibility when heated and low heat dissipation in both the planar and thickness directions. The resin sheet of Comparative Example 1 contained a linking filler but did not contain a plate-shaped filler; instead, it contained another filler (d1). The other filler (d1) was cardhouse-shaped and consisted of aggregates of plate-shaped aluminum oxide aggregated into spherical shapes.

[0168] In Comparative Example 2, the embedding rate R was high at 49.5%, and the flexibility of the resin sheet when heated was high. As shown in Figure 7, the surface of the polycarbonate substrate was heated to approximately 65-85°C in the region where four resistors in the same row were located, spanning these resistors, and this was similar in the region where two rows were located. However, in Comparative Example 2, the region that was heated in this way was narrower than in Example 1. Furthermore, as in Comparative Example 1, the region between these two rows was not heated to a high temperature. These results indicate that the resin sheet of Comparative Example 2, like the resin sheet of Comparative Example 1, had lower heat dissipation in the planar direction than the resin sheet of Example 1. On the other hand, as shown in Table 1, when comparing the thermocouple detection temperatures for the same resistors in Comparative Example 2 and Test Example 1, the detection temperatures in Comparative Example 2 were all higher than those in Test Example 1, similar to Comparative Example 1, indicating that the resin sheet of Comparative Example 2 had lower heat dissipation than the test resin sheet (commercially available thermally conductive sheet) used in Test Example 1. Furthermore, in Comparative Example 2, the detected temperatures were higher than in Comparative Example 1, indicating that the resin sheet of Comparative Example 2 had lower heat dissipation than the resin sheet of Comparative Example 1. Thus, the resin sheet of Comparative Example 2 had lower heat dissipation in both the planar and thickness directions. The resin sheet of Comparative Example 2 contained a linking filler but did not contain a plate-shaped filler; instead, it contained another filler (d2). The other filler (d2) was a polyhedral aluminum oxide filler.

[0169] The relative permittivity of the resin sheets in Comparative Examples 1 and 2 did not satisfy the condition of being 4 or less in both cases of 1 GHz and 10 GHz frequencies. The density of the resin sheets in Comparative Examples 1 and 2 was 2 g / cm³. 3 The following conditions were not met.

[0170] The test resin sheet (a commercially available thermally conductive sheet) used in Test Example 1 lacked flexibility when heated, making it impossible to cover or embed the heating element over a wider area. In Test Example 1, as shown in Figure 8, the surface of the polycarbonate substrate was heated to approximately 60-80°C in the region where four resistors in the same row were located, spanning these resistors, and this was similar in the region where two rows were located. However, in Test Example 1, the region that was heated in this way was smaller than in Example 1. Furthermore, the region between these two rows was not heated to a high temperature. These results indicated that the resin sheet in Test Example 1 had lower heat dissipation in the planar direction than the resin sheet in Example 1. As described above, when comparing the thermocouple-detected temperatures between identical resistors and between circuit surfaces of the circuit boards in Test Example 1 and Example 1, the detected temperatures were higher in Test Example 1 than in Example 1, indicating that the test resin sheet in Test Example 1 had lower heat dissipation than the resin sheet in Example 1.

[0171] [Example 2] <<Manufacturing of resin sheets>> A single-layer resin sheet (1500 μm thick) was manufactured using the same method as in Example 1, except that the amount of pelletized resin composition used was changed. In other words, the resin sheet in this example differed from the resin sheet in Example 1 only in its thickness.

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

[0173] A circuit board equipped with resistors and thermocouples was prepared, the same as in Example 1 (shown in Figure 4). Next, all eight resistors on the circuit board were covered collectively with the single resin sheet (1500 μm thick) obtained above, on the entire surface opposite to the circuit board side, via thermocouples if present, and then pressed down. As a result, the thermocouples on the resistors were positioned between the resistors and the resin sheet. Furthermore, a single polycarbonate substrate (2000 μm thick) was placed on the entire surface of the resin sheet opposite to the resistor side after covering. Thus, a test circuit board for evaluating the heat dissipation performance of the resin sheet was fabricated.

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

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

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

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

[0178] <<Checking the resistor temperature without a resin sheet>> [Test Example 2] The test was conducted 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.

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

[0180] [Table 2]

[0181] As is clear from the results above, when comparing the thermocouple-detected temperatures between identical resistors and between circuit sides of the circuit board in Examples 1 and 2 and Test Example 2, 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 comparing the thermocouple-detected temperatures between identical resistors and between circuit board surfaces in Examples 1-2 and Test Example 3, the detected temperatures in Examples 1-2 were lower than in Test Example 3. This indicates that the resin sheets in Examples 1-2 have higher heat dissipation properties not only in the surface direction but also in the thickness direction compared to the thermal interface material sheet in Test Example 3. The thermal interface material sheet in Test Example 3 had inferior embedding properties compared to the resin sheets in Examples 1-2. In the evaluation described above, the heat dissipation performance of the resin sheet relative to the heating element (resistor) was simply confirmed without embedding the heating element in the resin sheet. However, it was inferred that the resin sheet of Example 2, like the resin sheet of Example 1, would also exhibit high heat dissipation performance when the heating element is covered over a wider area, and preferably embedded. Thus, it was confirmed that the resin sheet of Example 2 has high flexibility when heated, high heat dissipation performance in both the planar and thickness directions, and can be used to construct a new heat dissipation structure.

[0182] Furthermore, when comparing the thermocouple-detected temperatures between identical resistors and between circuit board surfaces in Example 1 and Example 2, the detected temperature in Example 2 was lower than in Example 1. This was because, in Example 2, the embedding distance of the resin sheet was longer than in Example 1, resulting in a higher heat dissipation effect from the resin sheet.

[0183] [Example 3] <<Manufacturing of resin sheets>> A single-layer resin sheet (1500 μm thick) was manufactured using the same method as in Example 1, except that the content of the components in the resin sheet was changed as shown in Table 3, and the amount of pelletized resin composition used was also changed.

[0184] <<Evaluation of resin sheets>> <Calculation of embedding ratio R> The embedding ratio R was calculated for the resin sheet obtained above using the same method as in Example 1. The results are shown in Table 3.

[0185] <Confirmation of heat dissipation properties of resin sheets (3)> The resin sheet obtained above (thickness 1500 μm) was cut into pieces measuring 5 cm x 5 cm.

[0186] A single resistor was placed on the circuit surface of a circuit board. The height of this resistor (i.e., the distance between the top surface of the resistor (the side opposite to the circuit board) and the circuit surface of the circuit board) was 1.2 mm. Next, a thin-wire thermocouple was placed in relation to this resistor. Furthermore, one thin-wire thermocouple was placed on the side of the circuit board opposite to the circuit side (the back side), in the area directly below the resistor.

[0187] Next, the entire surface of the resistor on the circuit board, opposite to the circuit board side, was covered with the single resin sheet (1500 μm thick) obtained above, via a thermocouple, and then pressed down. As a result, the thermocouple on the resistor was positioned between the resistor and the resin sheet. Furthermore, a single polycarbonate substrate (2000 μm thick) was placed on the entire surface of the resin sheet opposite to the resistor side after covering. In this way, a test circuit board for evaluating the heat dissipation performance of the resin sheet was fabricated.

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

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

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

[0191] [Example 4] <<Manufacturing of resin sheets>> A single-layer resin sheet (1500 μm thick) was manufactured using the same method as in Example 1, except that the content of the components in the resin sheet was changed as shown in Table 3, and the amount of pelletized resin composition used was also changed.

[0192] <<Evaluation of resin sheets>> <Calculation of embedding ratio R> The embedding ratio R was calculated for the resin sheet obtained above using the same method as in Example 1. The results are shown in Table 3.

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

[0194] In the test circuit board used in this embodiment, the distance between the resistor-side surface of the polycarbonate substrate and the polycarbonate substrate-side surface of the resistor was found to be approximately 400 μm. In this test circuit board as well, similar to the case of Embodiment 3, the area of ​​the circuit board-side surface of the resin sheet that was not in contact with the resistor was in contact with the circuit board (more specifically, the circuit surface), and the resistor was completely embedded by the resin sheet.

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

[0196] <<Checking the resistor temperature without a resin sheet>> [Test Example 4] The test was conducted 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.

[0197] <<Confirmation of heat dissipation properties of thermal interface material sheet>> [Test Example 5] A circuit board equipped with resistors and thermocouples, the same as in Example 3, was prepared. Next, the entire surface of the resistor on the circuit board, opposite to the circuit board side, was covered with the same thermal interface material (TIM) sheet used in Test Example 1, via a thermocouple, and then pressed down. That is, in this test example, unlike in 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 to the resistor side after covering. In this way, a test circuit board for evaluating the heat dissipation performance of the thermal interface material sheet was fabricated. In this test example, the distance between the circuit side of the test circuit board and the resistor side (circuit side) of the polycarbonate substrate was the same as in Example 3.

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

[0199]

Table 3

[0200] As is clear from the above results, when comparing the detected temperatures by thermocouples between resistors and between the back surfaces of circuit boards in Examples 3 to 4 and Test Example 4, the detected temperatures in Examples 3 to 4 were significantly lower than those in Test Example 4. This was because no heat dissipation structure was provided in Test Example 4. Furthermore, when comparing the detected temperatures by thermocouples between resistors and between the back surfaces of circuit boards in Examples 3 to 4 and Test Example 5, the detected temperatures in Examples 3 to 4 were lower than those 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 heat interface material sheet of Test Example 5. The heat interface material sheet of Test Example 5 was inferior in embedding property 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 during heating, high heat dissipation properties in both the surface direction and the thickness direction, and could form a new heat dissipation structure.

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

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

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

[0204] The relative permittivity of the resin sheets in Examples 3 and 4 satisfied the condition of being 4 or less in both cases of frequencies of 1 GHz and 10 GHz. The dielectric loss tangent of the resin sheets in Examples 3 and 4 satisfied the condition of being less than 0.01 in both the 1 GHz and 10 GHz cases. The density of the resin sheets in Examples 3 and 4 was 2 g / cm³. 3 The following conditions were met: [Industrial applicability]

[0205] The present invention can be used to construct a new heat dissipation structure in electronic devices equipped with a CPU, and is not limited to CPUs; it can also be used to construct a heat dissipation structure in other devices equipped with heat-generating elements similar to those of a CPU. [Explanation of symbols]

[0206] 1. Resin sheet 3. Cabinet 4. Heat spreader 5. Heating element 6. Connection part 7. Circuit board 8... weight 9. Pressing material 10... Test specimens D S ...surface direction of the resin sheet D T ...The thickness of the resin sheet is directional T0... Thickness of the test specimen T1... Thickness of the test specimen at the pressurized area after heating and pressurizing.

Claims

1. It is a resin sheet, The resin sheet comprises a thermoplastic resin, a plate-shaped filler, and a connecting filler. A resin sheet in which the average particle size of the linked filler is 2 μm or less.

2. It is a resin sheet, The resin sheet comprises a thermoplastic resin, a plate-shaped filler, and a connecting filler. The average particle size of the linked filler is 2 μm or less. A single resin sheet, or a laminate of two or more resin sheets, with a thickness of T ０ Using the test specimen, a pressure of 12 kPa is applied to the test specimen in the thickness direction of the test specimen for 10 minutes in an environment of 100°C, and the thickness T of the test specimen is measured at the point where the pressure is applied. １ When measured, the following formula is used: R=(T ０ -T １ ) / T ０ ×100 A resin sheet with an embedding ratio R of 30% or more, calculated using [a specific method / tool].

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

4. The resin sheet according to claim 1 or 3, wherein 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 0.01 or less.

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

6. The resin sheet according to claim 1 or 3, wherein the connecting filler is made of 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 the connecting filler to the content of the plate-shaped filler is 60 to 140% by volume.

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

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

11. The resin sheet according to claim 2 or 10, wherein 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 0.01 or less.

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

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

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

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

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

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