Resin sheet

Abstract

A novel resin sheet (1) capable of constituting a novel heat dissipation structure having a high heat dissipation effect comprises a thermoplastic resin, a plate-shaped filler, and a connecting filler having an average particle diameter of 2 [mu] m or less. When a test piece (10) having a thickness of T0 and one or more of the resin sheets (1) is used, a pressure of 12 kPa is applied to the test piece (10) for 10 minutes in the thickness direction of the test piece (10) in an environment of 100 DEG C, and the thickness T1 of the test piece (10) at the site where the pressure is applied may be measured, the embedding rate R calculated from the following formula: R = (T0-T1) / T0 * 100 may be 30% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a resin sheet.

[0002] This application claims priority on the basis of Japanese Patent Application No. 2023-98720 filed in Japan on June 15, 2023, and Japanese Patent Application No. 2023-148498 filed in Japan on September 13, 2023, the contents of which are incorporated herein by reference. BACKGROUND

[0003] A central processing unit (CPU, abbreviated as "CPU" in the present specification) is one of representative devices constituting a computer. The amount of heat generated by a CPU increases dramatically when the computer is in operation. In response to this, in recent years, along with the high performance, miniaturization, and light weight of electronic devices, the high-density mounting of semiconductor packages, the high integration of LSIs (Large Scale Integrated Circuits), and the high speed of processing have been progressing, and countermeasures against heat generated in electronic devices have become extremely important.

[0004] In general electronic devices, a heat spreader is attached to a CPU provided on a circuit board via a thermal interface material (TIM, abbreviated as "TIM" in the present specification), and the heat spreader is provided in contact with a heat sink. Thereby, in the electronic device, heat generated in the CPU is conducted to the heat spreader via the TIM, and further, the heat is conducted in the plane direction of the heat spreader which is a plate, and the heat is released to the outside of the electronic device via the heat sink (see Patent Literature 1).

[0005] In the past, the reason why such a heat dissipation structure is adopted for a CPU is as follows. That is, a heat spreader is composed of metal or graphite, etc., and has high thermal conductivity and high heat dissipation in the plane direction, but does not have followability to the cooling object (CPU) and does not have sufficient adhesion to the cooling object (CPU), and does not have insulation. On the other hand, a TIM has a certain degree of followability to the cooling object (CPU) and has good adhesion, and has insulation, but has insufficient thermal conductivity. Therefore, by using these (heat spreader and TIM) in combination and adopting the above heat dissipation structure, these shortcomings are complemented.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: International Publication No. 2018 / 139364. SUMMARY

[0009] TECHNICAL PROBLEM TO BE SOLVED BY THE INVENTION

[0010] However, in such conventional electronic devices, as long as the TIM is a necessary structure, the heat dissipation structure is limited, and the structure of the electronic device is also limited. Then, as an alternative to the TIM, if the insulating property and the followability are taken into consideration, a resin sheet is suitable, but there has been no resin sheet with a high heat dissipation effect so far.

[0011] In addition, the description has been made so far with the CPU as an example, but the same problem can occur in other devices having the same heat generating body as the CPU.

[0012] The present application has an object to provide a novel resin sheet that can constitute a novel heat dissipation structure with a high heat dissipation effect.

[0013] Means for solving the technical problem

[0014] The present application is configured as follows.

[0015] [1] A resin sheet, wherein the resin sheet comprises a thermoplastic resin, a plate-shaped filler, and a bonding filler, and the average particle diameter of the bonding filler is 2 μm or less.

[0016] [2] A resin sheet, wherein the resin sheet comprises a thermoplastic resin, a plate-shaped filler, and a bonding filler, and the average particle diameter of the bonding filler is 2 μm or less, and when a test piece having a thickness of TO is prepared using one piece of the resin sheet or a laminate of two or more pieces of the resin sheet, and a pressure of 12 kPa is applied to the test piece in the thickness direction of the test piece for 10 minutes in an environment at 100°C, the embedded rate R calculated from the following formula: R = (TO - Tl) / TO x 100, at the portion where the pressure is applied, is 30% or more.

[0017] [3] The resin sheet according to [1], wherein the relative dielectric constant of the resin sheet is 4 or less at a frequency of 10 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method.

[0018] [4] The resin sheet according to [1] or [3], wherein the dielectric loss tangent of the resin sheet is 0.01 or less at a frequency of 10 GHz measured in accordance with the TM0m0 mode cavity resonator perturbation method.

[0019] [5] The resin sheet according to [1], [3], or [4], wherein the plate-shaped filler is composed of boron nitride or aluminum oxide.

[0020] [6] The resin sheet according to any one of [1] and [3] to [5], wherein the bonding filler is composed of magnesium hydroxide.

[0021] [7] The resin sheet according to any one of [1] and [3] to [6], wherein the aforementioned thermoplastic resin is an ethylene-vinyl acetate copolymer.

[0022] [8] The resin sheet according to any one of [1] and [3] to [7], wherein, in the aforementioned resin sheet, the proportion of the aforementioned binding filler with respect to the content of the aforementioned plate-like filler is 60 to 140 vol%.

[0023] [9] The resin sheet according to any one of [1] and [3] to [8], wherein the average particle diameter of the aforementioned plate-like filler is 5 μm or more.

[0024]

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

[0025]

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

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

[0026]

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

[10] or

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

[0027]

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

[10] to

[12] , wherein the aforementioned binding filler is composed of magnesium hydroxide.

[0028]

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

[10] to

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

[0029]

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

[10] to

[14] , wherein, in the aforementioned resin sheet, the proportion of the aforementioned binding filler with respect to the content of the aforementioned plate-like filler is 60 to 140 vol%.

[0030]

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

[10] to

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

[0031] Effects of the Invention

[0032] According to the present application, it is possible to provide a novel resin sheet that can constitute a novel heat dissipation structure having a high heat dissipation effect. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1Ais a sectional view for schematically illustrating a method of calculating an embedding rate R of a test piece of a resin sheet according to an embodiment of the present application, and is a sectional view of a laminate of the test piece, a press-in material, and a weight before heating and pressurization.

[0034] Figure 1B is a sectional view for schematically illustrating a method of calculating an embedding rate R of a test piece of a resin sheet according to an embodiment of the present application, and is a sectional view of a laminate of the test piece, a press-in material, and a weight immediately after heating and pressurization.

[0035] Figure 2A is a sectional view for schematically illustrating an example of a method of using a resin sheet according to an embodiment of the present application, and shows a state before covering a heat generating body with the resin sheet.

[0036] Figure 2B is a sectional view for schematically illustrating an example of a method of using a resin sheet according to an embodiment of the present application, and shows a state before covering a heat generating body with the resin sheet. Figure 2A

[0037] Figure 3A is a sectional view for schematically illustrating another example of a method of using a resin sheet according to an embodiment of the present application, and shows a state before covering a heat generating body with the resin sheet.

[0038] Figure 3B is a sectional view for schematically illustrating another example of a method of using a resin sheet according to an embodiment of the present application, and shows a state before covering a heat generating body with the resin sheet. Figure 3A

[0039] Figure 4 is a plan view for schematically illustrating a position of a resistor and a thermocouple on a circuit board when heat dissipation of a resin sheet or a test resin sheet with respect to a heat generating body is confirmed in Examples 1 to 2, Comparative Examples 1 to 2, and Test Examples 1 to 3.

[0040] Figure 5 is image data showing a result of confirming heat dissipation of a resin sheet with respect to a heat generating body in Example 1.

[0041] Figure 6 is image data showing a result of confirming heat dissipation of a resin sheet with respect to a heat generating body in Comparative Example 1.

[0042] Figure 7 is image data showing a result of confirming heat dissipation of a resin sheet with respect to a heat generating body in Comparative Example 2.

[0043] Figure 8 is image data showing a result of confirming heat dissipation of a test resin sheet with respect to a heat generating body in Test Example 1. DETAILED DESCRIPTION​​

[0044] <<Resin Sheet (Solution 1)>>

[0045] According to an embodiment of the present invention, the resin sheet of the first aspect comprises thermoplastic resin, plate-shaped filler and connecting filler, wherein the average particle size of the connecting filler is 2 μm or less. A test piece with a thickness T0 is used, consisting of one or more of the aforementioned resin sheets and a laminate of the aforementioned resin sheets. At an environment of 100°C, a pressure of 12 kPa is applied to the test piece in the thickness direction for 10 minutes. When the thickness T1 of the test piece at the location where the aforementioned pressure is applied is measured, the embedment rate R calculated by the following formula: R = (T0 - T1) / T0 × 100 is 30% or more.

[0046] The resin sheet of the first embodiment, because it contains the aforementioned plate-shaped filler and connecting filler, has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and its thickness direction. Furthermore, the resin sheet of the first embodiment contains a thermoplastic resin with an embedding ratio R of 30% or more and high flexibility when heated. By using the resin sheet of the first embodiment with these characteristics to cover (preferably embed) heat-generating elements such as CPUs (central processing units), novel heat dissipation structures 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; heat dissipation structures can also be constructed in other devices with the same heat-generating elements as CPUs, and a high effect of suppressing heat generation can also be obtained.

[0047] In addition, in this specification, the "direction parallel to the surface" is sometimes referred to as the "surface direction", which is not limited to resin sheets.

[0048] The resin sheet of the first scheme is insulating.

[0049] <Thermoplastic Resins>

[0050] The aforementioned resin sheet, by containing the aforementioned thermoplastic resin, is able to maintain a sheet shape and has conformability and adhesion to its applicable object.

[0051] There are no particular limitations on the aforementioned thermoplastic resin as long as it can impart the aforementioned resin sheet with flexibility when heated and achieve the aforementioned embedment ratio R.

[0052] The aforementioned resin sheet can be manufactured, for example, by molding (pressurized heating molding) the resin composition used to manufacture the aforementioned resin sheet. In this case, it is preferable that the aforementioned thermoplastic resin has a melting point lower than the heating temperature (molding temperature) during molding of the aforementioned resin composition. By molding the aforementioned resin composition at a temperature higher than the melting point of the aforementioned thermoplastic resin, a resin sheet with higher uniformity can be obtained.

[0053] The melting point of the aforementioned thermoplastic resin is preferably below 90°C, for example, it can be either below 80°C or below 70°C. By using a thermoplastic resin with a melting point below the aforementioned upper limit, resin sheets with higher uniformity can be obtained.

[0054] There is no particular limitation on the lower limit of the melting point of the aforementioned thermoplastic resins. For example, thermoplastic resins with a melting point above 35°C are easier to obtain or manufacture.

[0055] In one embodiment, the melting point of the aforementioned thermoplastic resin can be, for example, any one of 35–90°C, 35–80°C, and 35–70°C. However, these are just examples of the melting points of thermoplastic resins.

[0056] The melt flow rate (sometimes referred to as "MFR" in this specification) of the aforementioned thermoplastic resin is preferably 1 to 40 g / 10 min, for example, it can be any one of 5 to 40 g / 10 min and 10 to 40 g / 10 min. When the MFR of the thermoplastic resin is above the aforementioned lower limit, the resin sheet becomes more adaptable to its applicable object; for example, when covering a heating element with the aforementioned resin sheet, it is easier to cover the heating element with the resin sheet. When the MFR of the thermoplastic resin is below the aforementioned upper limit, the shape of the aforementioned resin sheet can be maintained more stably.

[0057] Unless otherwise specified, MFR in this manual refers to the value measured in accordance with JIS K7210:1999.

[0058] Preferred thermoplastic resins include, for example, ethylene-vinyl acetate copolymer (EVA). EVA has a lower melting point than other resins and exhibits endothermic properties when heated to or near its melting point. Therefore, the aforementioned resin sheet containing ethylene-vinyl acetate copolymer has higher heat dissipation due to its latent heat storage function. Furthermore, ethylene-vinyl acetate copolymer possesses flexibility, impact resistance, and adhesiveness, making it easy for the resin sheet to adhere tightly to the heating element when covered. Moreover, ethylene-vinyl acetate copolymer is polar, thus it can be compounded with flame retardants (e.g., magnesium hydroxide), easily imparting flame retardancy to the resin sheet.

[0059] In the aforementioned ethylene-vinyl acetate copolymer, the ratio (parts by mass) of the constituent units derived from vinyl acetate to the total amount (parts by mass) of the constituent units (sometimes referred to as "vinyl acetate content" in this specification) is preferably 10-40% by mass, for example, either 20-40% by mass or 30-40% by mass. When the aforementioned ratio (vinyl acetate content) is at or above the aforementioned lower limit, the resin sheet's adaptability and fit to its applicable objects become higher. For example, when the aforementioned resin sheet covers a heating element, it is easy to cover the heating element with the resin sheet and the resin sheet easily adheres to the heating element. When the aforementioned ratio is below the aforementioned upper limit, the workability during the manufacture of the aforementioned resin sheet becomes higher.

[0060] The aforementioned thermoplastic resin contained in the aforementioned resin sheet may be only one type or two or more types. In the case of two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0061] From the viewpoint of obtaining the effects of the present invention more significantly, it is preferable that the thermoplastic resin contained in the aforementioned resin sheet is an ethylene-vinyl acetate copolymer.

[0062] In the aforementioned resin sheet, the ratio of the content (parts by mass) of the aforementioned thermoplastic resin to the total mass (parts by mass) of the aforementioned resin sheet ([content (parts by mass) of thermoplastic resin in the resin sheet] / [total mass (parts by mass) of the resin sheet]×100) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. By setting the aforementioned ratio to the aforementioned lower limit value or above, the effect obtained by including thermoplastic resin in the resin sheet becomes more significant.

[0063] In the aforementioned resin sheet, the ratio of the content (parts by mass) of the aforementioned thermoplastic resin to the total mass (parts by mass) of the aforementioned resin sheet is preferably 45% by mass or less, more preferably 40% by mass or less. By setting the aforementioned ratio to the aforementioned upper limit, the effect obtained by including components other than thermoplastic resin in the resin sheet becomes more significant.

[0064] In one embodiment, the aforementioned ratio can be any one of 20-45% by mass, 25-45% by mass, and 30-45% by mass, or any one of 20-40% by mass, 25-40% by mass, and 30-40% by mass. However, these are just examples of the aforementioned ratios.

[0065] Typically, the aforementioned ratio is the same as the ratio of the content (parts by mass) of the aforementioned thermoplastic resin in the resin composition described later to the total content (parts by mass) of the components that do not vaporize at room temperature ([content (parts by mass) of the thermoplastic resin in the resin composition] / [total content (parts by mass) of the components that do not vaporize at room temperature in the resin composition]×100).

[0066] In this instruction manual, "room temperature" refers to the temperature at which no special cooling or heating is required, i.e., the normal temperature, such as 15 to 25°C.

[0067] <plate packing>

[0068] By incorporating the aforementioned plate-shaped filler into the resin sheet, its heat dissipation becomes higher. In the resin sheet, the surface direction of the plate-shaped filler tends to be oriented in the same direction as or close to the surface direction of the resin sheet. Therefore, in particular, the thermal conductivity of the resin sheet in its surface direction becomes higher, and its heat dissipation in its surface direction becomes higher.

[0069] For example, when using fillers other than plate-shaped fillers, such as polyhedral fillers or card-roof fillers (fillers in which plate-shaped fillers agglomerate to form secondary particles), instead of plate-shaped fillers, the heat dissipation of the resin sheet in the face direction decreases. Moreover, card-roof fillers significantly reduce the flexibility of the resin sheet when heated.

[0070] The aspect ratio (particle size of the plate filler / thickness of the plate filler) of the aforementioned plate filler is preferably 10 to 50, for example, it can be any one of 10 to 30 and 30 to 50. With the aspect ratio of the plate filler in this range, the effect obtained by including the plate filler in the resin sheet becomes more pronounced.

[0071] As for the particle size of the aforementioned plate-shaped packing, for example, it can be the maximum value of the length of the line segment connecting two different points on the outer periphery of the plate-shaped packing.

[0072] The thickness of the aforementioned plate-shaped packing can be, for example, the maximum distance between the main surfaces of the plate-shaped packing.

[0073] As for the aspect ratio of the aforementioned plate-shaped packing, for example, the average aspect ratio of 50 randomly selected plate-shaped packings can be used.

[0074] The average particle size of the aforementioned plate-shaped packing is preferably 5 μm or more, for example, it can be either 6.5 μm or more or 8 μm or more. By having an average particle size of the plate-shaped packing of the aforementioned lower limit or above, the effect obtained by using plate-shaped packing becomes even greater.

[0075] There is no particular upper limit to the average particle size of plate-shaped packings. For example, plate-shaped packings with an average particle size of less than 15 μm are more readily available.

[0076] In one embodiment, the average particle size of the plate-shaped packing can be, for example, any one of 5–15 μm, 6.5–15 μm, and 8–15 μm. However, these are just examples of the average particle size of the plate-shaped packing.

[0077] Unless otherwise specified in this specification, "average particle size" refers to the particle size (D50) of 50% of the particles when the particle size distribution is determined by laser diffraction particle size distribution measurement method on a volume basis, and this is not limited to plate-shaped packings.

[0078] The thermal conductivity of the plate-shaped packing can be, for example, any one of 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.

[0079] There is no particular upper limit to the thermal conductivity of plate-shaped packings. For example, plate-shaped packings with a thermal conductivity of less than 400 W / m·K are more readily available.

[0080] In one embodiment, the thermal conductivity of the plate-shaped packing can be, for example, any one of 5–400 W / m·K, 10–400 W / m·K, 25–400 W / m·K, and 40–400 W / m·K. However, these are just examples of the thermal conductivity of the plate-shaped packing.

[0081] The thermal conductivity of the filler can be measured, for example, by fabricating a sintered body of the filler and using known thermal conductivity measuring devices such as the laser flash method or the hot plate method, or by using a thermophysical microscope, and is not limited to plate-shaped fillers.

[0082] From the viewpoint that it is easier to reduce the relative permittivity of the aforementioned resin sheet described later, the relative permittivity of the plate-shaped filler is preferably 5.5 or less, more preferably 4.5 or less.

[0083] On the other hand, there is no particular limit to the lower limit of the relative permittivity of plate-shaped packings. For example, plate-shaped packings with a relative permittivity of 3.5 or higher are easier to prepare or obtain.

[0084] Materials used as the aforementioned plate-shaped fillers include, for example, metal nitrides such as boron nitride and metal oxides such as aluminum oxide.

[0085] The aforementioned resin sheet may contain only one type of plate-shaped filler or two or more types. In the case of two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0086] The aforementioned plate-shaped filler is preferably composed of boron nitride (BN) or alumina (Al2O3) (i.e., boron nitride filler or alumina filler). In addition to high heat dissipation, the resin sheet containing such a plate-shaped filler also has better flowability during heating, and the resin sheet has greater adaptability to the target object. For example, when the aforementioned resin sheet covers the heating element, it is easy to cover the heating element with the resin sheet.

[0087] More preferably, the aforementioned plate-shaped filler is composed of boron nitride (BN) (i.e., boron nitride filler). In addition to the preferred characteristics described above, the resin sheet containing such plate-shaped filler also has further preferred characteristics, as described later, to further reduce its relative permittivity.

[0088] In the aforementioned resin sheet, the ratio of the content (volume parts) of the plate-shaped filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of plate-shaped filler in the resin sheet] / [total volume (volume parts) of the resin sheet]×100) is preferably 10% by volume or more, for example, it can be any one of 15% by volume or more, 20% by volume or more, and 25% by volume or more. By setting the aforementioned ratio to the aforementioned lower limit value or above, the effect obtained by using the plate-shaped filler becomes more significant.

[0089] In the aforementioned resin sheet, the ratio of the content (volume parts) of the plate-shaped filler to the total volume (volume parts) of the resin sheet is preferably 35% by volume or less, for example, it can be any one of 30% by volume or less, 25% by volume or less, and 20% by volume or less. By setting the aforementioned ratio to the aforementioned upper limit value, the effect obtained by using fillers other than plate-shaped fillers, such as the aforementioned connecting fillers, becomes even greater.

[0090] In one embodiment, the aforementioned ratio can be any one of 10-35% by volume, 15-35% by volume, 20-35% by volume, and 25-35% by volume; or any one of 10-30% by volume, 15-30% by volume, 20-30% by volume, and 25-30% by volume; or any one of 10-25% by volume, 15-25% by volume, and 20-25% by volume; or 10-20% by volume. However, these are just examples of the aforementioned ratios.

[0091] <Connecting Packing>

[0092] By including the aforementioned connecting filler in the resin sheet, its heat dissipation performance is improved. In the resin sheet, the connecting filler is widely distributed 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, thus linking the plate-shaped filler together. As a result, the thermal conductivity and heat dissipation performance of the resin sheet are both improved in both the planar and thickness directions. In particular, by including the connecting filler in the resin sheet, its thermal conductivity and heat dissipation performance in the thickness direction are both improved. When the resin sheet does not contain the connecting filler, the heat dissipation performance in the thickness direction does not become so high.

[0093] The average particle size of the aforementioned connecting packing is less than 2 μm. As a result, the plate-shaped packings are fully connected to each other by the connecting packing.

[0094] To achieve this effect, the average particle size of the connecting filler is preferably 1.5 μm or less, for example, either 1.2 μm or less or 0.9 μm or less.

[0095] There is no particular limit to the lower limit of the average particle size of the linker filler. For example, linker fillers with an average particle size of 0.5 μm or more are easier to obtain, and by using such linker fillers, the heat dissipation of the resin sheet can be improved more easily.

[0096] In one embodiment, the average particle size of the linking packing can be, for example, any one of 0.5–2 μm, 0.5–1.5 μm, 0.5–1.2 μm, and 0.5–0.9 μm. However, these are just examples of the average particle size of the linking packing.

[0097] The shape of the connecting filler is not particularly limited, but a planar shape is preferred, and a plate shape is more preferably preferred. By having a planar shape, especially a plate shape, the contact area between the connecting filler and the plate-shaped filler becomes larger. As mentioned above, the surface direction of the plate-shaped filler tends to be oriented in the same direction as or close to the surface direction of the resin sheet. Therefore, even if the connecting filler has a planar shape, there is a tendency for the contact area between the connecting filler and the plate-shaped filler to decrease as the overall shape of the connecting filler deviates from a plate shape. However, by having an average particle size of 2 μm or less, sufficient contact between the connecting filler and the plate-shaped filler can be maintained.

[0098] The binding filler is preferably a non-agglomerated material (not an aggregate). The less binding filler content of the resin sheet that acts as an aggregate, the higher the fluidity of the resin sheet during heating, and the higher the adaptability of the resin sheet to the applicable object. For example, when the aforementioned resin sheet is used to cover the heating element, it is easy to cover the heating element with the resin sheet.

[0099] The thermal conductivity of the connecting filler can be, for example, any one of 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.

[0100] There is no particular upper limit to the thermal conductivity of the bonding packing. For example, bonding packing with a thermal conductivity of less than 400 W / m·K is more readily available.

[0101] In one embodiment, the thermal conductivity of the connecting packing can be, for example, any one of 5–400 W / m·K, 10–400 W / m·K, 25–400 W / m·K, and 40–400 W / m·K. However, these are just examples of the thermal conductivity of the connecting packing.

[0102] Materials used as connecting fillers include, for example, metal hydroxides such as magnesium hydroxide.

[0103] The surface of the linker filler may or may not be treated with a surface treatment agent. By using a surface-treated linker filler, for example, the affinity of the linker filler with resins such as thermoplastic resins is improved, and the flowability of the aforementioned resin sheet is improved, thus increasing the conformability and adhesion of the resin sheet to its applicable object.

[0104] Surface treatments used as binding fillers include, for example, surface treatments based on fatty acids or organosilicon compounds (silane coupling agents).

[0105] The aforementioned resin sheet may contain only one type of binder or two or more types. When there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0106] Preferably, the aforementioned binder is composed of magnesium hydroxide (Mg(OH)2) (i.e., magnesium hydroxide filler). Magnesium hydroxide is also a flame retardant, therefore, resin sheets containing this binder not only have high heat dissipation but also high flame retardancy.

[0107] The aforementioned resin sheets containing magnesium hydroxide filler, etc., impart flame retardancy, for example, meeting UL94 standard levels V-0, V-1 or V-2.

[0108] In the aforementioned resin sheet, the ratio of the binder content to the plate filler content ([binding filler content of resin sheet (volume parts)] / [plate filler content of resin sheet (volume parts)] × 100) is preferably 60% by volume or more, for example, it can be any one of 65% by volume or more, 70% by volume or more, 90% by volume or more, and 200% by volume or more. By setting the aforementioned ratio to the aforementioned lower limit value or above, the effect obtained by using the binder becomes more significant.

[0109] In the aforementioned resin sheet, the ratio of the content of the linking filler to the content of the plate-shaped filler is preferably 300% by volume or less, for example, it can be any one of 250% by volume or less, 140% by volume or less, 110% by volume or less, and 80% by volume or less. By setting the aforementioned ratio to the aforementioned upper limit value, the effect obtained by using fillers other than the linking filler, such as the aforementioned plate-shaped filler, becomes even greater.

[0110] In one embodiment, the aforementioned ratio is preferably 60-300% by volume, for example, any one of 65-300% by volume, 70-300% by volume, 90-300% by volume, and 200-300% by volume; or any one of 60-250% by volume, 65-250% by volume, 70-250% by volume, and 90-250% by volume; or any one of 60-140% by volume, 65-140% by volume, 70-140% by volume, and 90-140% by volume; or any one of 60-110% by volume, 65-110% by volume, 70-110% by volume, and 90-110% by volume; or any one of 60-80% by volume, 65-80% by volume, and 70-80% by volume. However, these are just examples of the aforementioned ratios.

[0111] In the aforementioned resin sheet, the ratio of the content (volume parts) of the linking filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of the linking filler in the resin sheet] / [total volume (volume parts) of the resin sheet]×100) is preferably within a numerical range satisfying the ratio of the content of the linking filler to the content of the plate-shaped filler described above. For example, it is preferably 6% by volume or more, and can be any one of 9.8% by volume or more, 14% by volume or more, 20% by volume or more, and 25% by volume or more. By setting the aforementioned ratio to the aforementioned lower limit value or above, the effect obtained by using the linking filler becomes higher.

[0112] In the aforementioned resin sheet, the ratio of the content (volume parts) of the linking filler to the total volume (volume parts) of the resin sheet is preferably 49% by volume or less, for example, either 33% by volume or less or 21% by volume or less. By setting the aforementioned ratio to the aforementioned upper limit, the effect obtained by using fillers other than linking fillers, such as the aforementioned plate-shaped filler, becomes even greater.

[0113] In one embodiment, the aforementioned proportions can be any one of 6–49% by volume, 9.8–49% by volume, 14–49% by volume, 20–49% by volume, and 25–49% by volume; or any one of 6–33% by volume, 9.8–33% by volume, 14–33% by volume, and 20–33% by volume; or any one of 6–21% by volume, 9.8–21% by volume, and 14–21% by volume. However, these are just examples of the aforementioned proportions.

[0114] <Other Ingredients>

[0115] The aforementioned resin sheet may contain other components that are not among the aforementioned thermoplastic resin, the aforementioned plate-shaped filler, and the aforementioned connecting filler, without impairing the effects of the present invention.

[0116] The other ingredients mentioned above are not particularly limited and can be selected arbitrarily according to the purpose.

[0117] The aforementioned resin sheet may contain only one or more of the aforementioned other components. In the case of two or more components, their combination and ratio can be arbitrarily selected according to the purpose.

[0118] Other components mentioned above include, for example, additives known in the field.

[0119] Examples of such additives include antioxidants, antistatic agents, viscosity reducers, thickeners, infrared absorbers, ultraviolet absorbers, and anti-caking agents.

[0120] In the aforementioned resin sheet, the ratio of the total content (parts by mass) of the aforementioned thermoplastic resin, the aforementioned plate-shaped filler, and the aforementioned connecting filler to the total mass (parts by mass) of the aforementioned 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, for example, it can be any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. By having the aforementioned ratio at or above the aforementioned lower limit value, the heat dissipation performance and the flexibility during heating of the aforementioned resin sheet become more evenly improved. On the other hand, the aforementioned ratio is 100% by mass or less.

[0121] Typically, the aforementioned ratio is the same as the ratio of the total content (parts by mass) of the aforementioned thermoplastic resin, the aforementioned plate filler and the aforementioned connecting filler in the resin composition described later to the total content (parts by mass) of the components that do not vaporize at room temperature (([content of thermoplastic resin in the resin composition (parts by mass)] + [content of plate filler in the resin composition (parts by mass)] + [content of connecting filler in the resin composition (parts by mass)]) / [total content (parts by mass) of the components that do not vaporize at room temperature in the resin composition] × 100).

[0122] The thickness of the aforementioned resin sheet is preferably 100 μm or more, for example, it can be any one of 300 μm or more, 500 μm or more, 800 μm or more, and 1100 μm or more. By having the thickness of the resin sheet at or above the aforementioned lower limit, the heat dissipation performance of the resin sheet becomes higher.

[0123] On the other hand, the thickness of the aforementioned resin sheet is preferably 2000 μm or less, for example, it can be either 1500 μm or less or 1000 μm or less. By keeping the thickness of the resin sheet below the aforementioned upper limit, the flexibility of the resin sheet during heating becomes higher.

[0124] In one embodiment, the thickness of the aforementioned resin sheet can be, for example, any one of 100–2000 μm, 300–1500 μm, 500–1000 μm, and 800–1500 μm. However, these are just examples of the thickness of the resin sheet.

[0125] As will be described below, the thickness of the resin sheet is preferably adjusted according to the thickness of the object to which the resin sheet is intended.

[0126] <Characteristics of Resin Sheets>

[0127] [Embedding Rate R]

[0128] Using a single test piece of the aforementioned resin sheet with a thickness of T0, or a stack of two or more of the aforementioned resin sheets with a thickness of T0, a pressure of 12 kPa is applied to the test piece in the thickness direction for 10 minutes at an environment of 100°C. The thickness T1 of the test piece is measured at the location where the pressure is applied, using the following formula: R = (T0 - T1) / T0 × 100 The calculated embedment rate R is 30% or higher. The resin sheet of the first embodiment, with an embedment rate R within this range, exhibits high flexibility during heating. Therefore, the heating element can be well covered with the resin sheet.

[0129] The following, with reference to the attached figures, provides a more detailed explanation of the calculation method for the aforementioned embedment rate R.

[0130] Figure 1A and Figure 1B This is a cross-sectional view used to schematically illustrate the calculation method of the embedment rate R of the aforementioned test piece using the aforementioned resin sheet.

[0131] Furthermore, regarding the accompanying drawings used in the following description, for ease of understanding of the features of the invention, some parts that will be considered major parts are sometimes shown in enlarged form, and the size ratios of the constituent elements are not necessarily the same as in reality.

[0132] For example, to determine T1 (the thickness of the test piece at the pressurized area after heating and pressurization), such as Figure 1A As shown, the test piece 10 is placed on a flat surface, and the press-in material 9 is placed near the center of the exposed, upward-facing side surface 10a of the test piece 10. The press-in material 9 is a means of pressing the test piece 10 into contact with it and applying pressure.

[0133] The test piece 10 is one of the aforementioned resin sheets or a stack of two or more of the aforementioned resin sheets. Regardless of which type the test piece 10 is, the thickness of the test piece 10 in the thickness direction without pressure applied is T0.

[0134] T0 is not particularly limited. For example, it can be any of the following: above 500μm, above 1000μm, and above 1500μm, or below 3500μm, below 3000μm, and below 2500μm.

[0135] exist Figure 1A and Figure 1B The contents of test piece 10 (resin sheet) are omitted from the description. Figure 2A and Figure 2B In the following figures, the contents of the resin sheet are omitted from the cross-sectional view of the resin sheet in this embodiment.

[0136] The constituent material of the pressed material 9 is not particularly limited as long as it is hard; for example, various ceramics can be cited.

[0137] The shape of the pressed material 9 is not particularly limited as long as the contact part with the test piece 10 is planar. For example, it can be any shape such as prism, frustum, cylinder, truncated cone, elliptical cylinder, frustum, etc.

[0138] The area of ​​the contact surface (in other words, the pressing surface) 9b of the pressed material 9 with the test piece 10 only needs to be smaller than the area of ​​one side surface 10a of the test piece 10, preferably 0.05 to 0.30 times the area of ​​one side surface 10a of the test piece 10.

[0139] Then, a weight 8 is placed on the other side surface of the pressed material 9 in this state (the exposed upward surface that does not contact the side surface 10a of the test piece 10).

[0140] The weight 8 can be placed on a portion of the other side 9a of the pressed material 9, or it can be placed on the entire surface.

[0141] The weight 8 placed on the pressing material 9 can be one or more.

[0142] Thus, a stack 100 is formed by placing a weight 8 on the press-in material 9 and sequentially stacking the test piece 10, the press-in material 9, and the weight 8, thereby applying a pressure of 12 kPa to the test piece 10 in the thickness direction by the press-in material 9 and the weight 8.

[0143] Then, the laminate 100 in this state is immediately placed in an environment of 100°C and left to stand for 10 minutes.

[0144] Therefore, at 100°C, a pressure of 12 kPa was applied to the test piece 10 in the thickness direction for 10 minutes.

[0145] When the laminate 100 is placed in an environment of 100°C, the heated test piece 10 softens and is pressed in by the pressing material 9, and the contact portion between the test piece 10 and the pressing material 9 is recessed.

[0146] Then, immediately after 10 minutes, the thickness T1 of the test piece 10 at the pressure-applied location in the laminate 100 under heating and pressurization is measured.

[0147] Therefore, T0 and T1 can be measured, and using these measured values, the embedment rate R of the test piece 10 can be calculated using the aforementioned formula.

[0148] From the perspective of being able to easily cover the heating element with a resin sheet, the embedment rate R is preferably 35% or more, for example, it can be any one of 40% or more, 45% or more, and 50% or more.

[0149] On the other hand, there is no particular upper limit to the embedment ratio R. For example, resin sheets with embedment ratios R of 65% or less and 60% or less are easier to manufacture.

[0150] In one embodiment, the embedment rate R can be any one of 30-65%, 35-65%, 40-65%, 45%-65%, and 50-65%, or any one of 30-60%, 35-60%, 40-60%, and 45-60%. However, these are just examples of embedment rates R.

[0151] The embedding rate R of the aforementioned resin sheet can be adjusted, for example, by adjusting the types and contents of the components contained in the resin sheet, especially the types and contents of thermoplastic resins.

[0152] Thermal conductivity in the planar direction

[0153] The aforementioned resin sheet preferably has a thermal conductivity of 2 W / m·K or higher in the planar direction, more preferably 3 W / m·K or higher, and for example, 4 W / m·K or higher. The aforementioned resin sheet with a thermal conductivity of 2 W / m·K or higher than the aforementioned lower limit value exhibits high heat dissipation in the planar direction.

[0154] There is no particular upper limit to the thermal conductivity of the aforementioned resin sheet in the planar direction. For example, resin sheets with a thermal conductivity of 15 W / m·K or less can be more easily manufactured.

[0155] In one embodiment, the thermal conductivity of the aforementioned resin sheet in the planar direction can be, for example, any one of 2-15 W / m·K, 3-15 W / m·K, and 4-15 W / m·K.

[0156] The thermal conductivity of the resin sheet in the planar direction is more specifically the thermal conductivity of the resin sheet in a direction parallel to one or the other surface of the resin sheet, and is not limited to the aforementioned resin sheet.

[0157] The thermal conductivity of the resin sheet in the planar direction can be measured, for example, according to ISO 22007-2 by the hot plate method. For example, the aforementioned thermal conductivity can be measured using a hot plate thermophysical property measuring device (e.g., "TPS 2500 S", "TPS 500S", etc.) manufactured by Kyoto Electronics Co., Ltd.

[0158] The thermal conductivity of the aforementioned resin sheet in the planar direction can be adjusted, for example, by adjusting the type of the aforementioned thermoplastic resin and its content in the resin sheet, the type of the aforementioned plate-shaped filler and its content in the resin sheet, the type of the aforementioned connecting filler and its content in the resin sheet, and the thickness of the aforementioned resin sheet.

[0159] [Relative permittivity]

[0160] The relative permittivity of the aforementioned resin sheet at a frequency of 10 GHz, measured according to the TM0m0 mode cavity resonator perturbation method, is preferably 4 or less, for example, it can be any one of 3.75 or less, 3.65 or less, and 3.55 or less. The aforementioned resin sheet with a relative permittivity of less than or equal to the aforementioned upper limit at a frequency of 10 GHz has high insulation properties. For example, in the circuit of the object to which the aforementioned resin sheet is assembled, the effect of suppressing noise that generates electrical signals is high. From this perspective, the resin sheet assembled as a heat-generating element covering a circuit board is particularly suitable.

[0161] There is no particular limitation on the lower limit of the aforementioned relative permittivity at a frequency of 10 GHz. For example, the aforementioned resin sheet with a relative permittivity of 1 or higher at a frequency of 10 GHz can be more easily manufactured.

[0162] In one embodiment, the aforementioned relative permittivity at a frequency of 10 GHz can be, for example, any one of 1–4, 1–3.75, 1–3.65, and 1–3.55. However, these are just examples of the aforementioned relative permittivity at a frequency of 10 GHz.

[0163] The aforementioned relative permittivity at a frequency of 10 GHz is preferably a value measured at room temperature (e.g., at a temperature of 23 °C).

[0164] The relative permittivity of the aforementioned resin sheet at a frequency of 1 GHz, measured according to the perturbation method of the TM0m0 mode cavity resonator, is preferably 4 or less, for example, it can be either 3.9 or less or 3.8 or less. The aforementioned resin sheet with a relative permittivity of less than or equal to the aforementioned upper limit at a frequency of 1 GHz has high insulation properties. For example, in the circuit of the object to which the aforementioned resin sheet is assembled, the effect of suppressing noise that generates electrical signals is high. From this perspective, the resin sheet assembled as a heat-generating element covering a circuit board is particularly suitable.

[0165] There is no particular limitation on the lower limit of the aforementioned relative permittivity at a frequency of 1 GHz. For example, the aforementioned resin sheet with a relative permittivity of 1 or higher at a frequency of 1 GHz can be more easily manufactured.

[0166] In one embodiment, the aforementioned relative permittivity at a frequency of 1 GHz can be, for example, any one of 1 to 4, 1 to 3.9, and 1 to 3.8. However, these are just examples of the aforementioned relative permittivity at a frequency of 1 GHz.

[0167] The aforementioned relative permittivity at a frequency of 1 GHz is preferably a value measured at room temperature (e.g., at a temperature of 23 °C).

[0168] The relative permittivity of the aforementioned resin sheet can be adjusted by changing the type and content of the components contained in the resin sheet, without depending on the frequency.

[0169] [Dielectric loss tangent]

[0170] The dielectric loss tangent of the aforementioned resin sheet at a frequency of 10 GHz, measured according to the TM0m0 mode cavity resonator perturbation method, is preferably 0.01 or less, for example, it can be any one of 0.0065 or less, 0.0055 or less, and 0.0045 or less. The aforementioned resin sheet with a dielectric loss tangent in this range at a frequency of 10 GHz has high electromagnetic wave transmittance and is suitable for constructing electronic devices equipped with antennas.

[0171] There is no particular limitation on the lower limit of the aforementioned dielectric loss tangent at a frequency of 10 GHz. For example, the aforementioned resin sheet with a dielectric loss tangent of 0.001 or higher at a frequency of 10 GHz can be more easily manufactured.

[0172] In one embodiment, the dielectric loss tangent at a frequency of 10 GHz can be any one of 0.001–0.01, 0.001–0.0065, 0.001–0.0055, and 0.001–0.0045. However, these are just examples of the dielectric loss tangent at a frequency of 10 GHz.

[0173] The aforementioned dielectric loss tangent at a frequency of 10 GHz is preferably a value measured at room temperature (e.g., at a temperature of 23 °C).

[0174] The dielectric loss tangent of the aforementioned resin sheet at a frequency of 1 GHz, measured according to the perturbation method of the TM0m0 mode cavity resonator, is preferably 0.01 or less, for example, it can be either 0.009 or less or 0.008 or less. The aforementioned resin sheet with a dielectric loss tangent in this range at a frequency of 1 GHz has high radio wave transmittance and is suitable for constructing electronic devices with antennas.

[0175] There is no particular limitation on the lower limit of the aforementioned dielectric loss tangent at a frequency of 1 GHz. For example, the aforementioned resin sheet with a dielectric loss tangent of 0.001 or higher at a frequency of 1 GHz can be more easily manufactured.

[0176] In one embodiment, the dielectric loss tangent at a frequency of 1 GHz can be any one of 0.001–0.01, 0.001–0.009, and 0.001–0.008. However, these are just examples of the dielectric loss tangent at a frequency of 1 GHz.

[0177] The aforementioned dielectric loss tangent at a frequency of 1 GHz is preferably a value measured at room temperature (e.g., at a temperature of 23 °C).

[0178] The dielectric loss tangent of the aforementioned resin sheet can be adjusted by changing the type and content of the components contained in the resin sheet, without depending on the frequency.

[0179] In the aforementioned resin sheet, the relative permittivity at a frequency of 10 GHz and the relative permittivity at a frequency of 1 GHz are preferably both within the above-mentioned numerical range.

[0180] 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-mentioned numerical range.

[0181] In the aforementioned 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-mentioned numerical range.

[0182] [density]

[0183] The density of the aforementioned resin sheet is preferably 2 g / cm³. 3 For example, it could be 1.7 g / cm³. 3 The following describes various electronic devices constructed using this type of resin sheet. Besides suppressing heat generation, their lightweight nature makes them suitable for, for example, constructing portable electronic devices.

[0184] There is no specific lower limit to the density of the aforementioned resin sheets. For example, a density of 1 g / cm³... 3 The aforementioned resin sheets can be more easily produced.

[0185] In one embodiment, the density of the aforementioned resin sheet can be, for example, 1 to 2 g / cm³. 3 and 1~1.7g / cm 3Any one of them. However, these are examples of the density of the aforementioned resin sheets.

[0186] The density of the aforementioned resin sheet can be adjusted, for example, by adjusting the types and amounts of the components contained in the resin sheet.

[0187] The density of the aforementioned resin sheet can be determined by known methods, for example, in accordance with JIS K7112:1999 or JIS K 0061:2022 (density gradient tube method).

[0188] The aforementioned resin sheet can be a resin sheet irradiated with electron beams. In this case, the aforementioned resin sheet is preferably an irradiated resin sheet subjected to electron beams under an absorption line intensity of 20–300 kGy. The accelerating voltage for electron beam irradiation is preferably 100–300 kV.

[0189] By irradiating the aforementioned resin sheet with electron beams, a portion of the resin sheet is cross-linked, thereby improving the heat resistance and repairability of the resin sheet.

[0190] <<Resin Compositions and Their Manufacturing Methods>>

[0191] The resin sheet of the first embodiment can be manufactured, for example, by using a resin composition comprising the aforementioned thermoplastic resin, the aforementioned plate-shaped filler, the aforementioned connecting filler, and, as needed, the aforementioned other components (in this specification, sometimes referred to as the "resin composition of the first embodiment").

[0192] In addition to the components mentioned above, the aforementioned resin composition may also contain a solvent. The operability of the aforementioned resin composition may sometimes be improved when a solvent is included.

[0193] In this specification, unless otherwise specified, the term "solvent" refers not only to components that can dissolve the solute in solution, but also to components that serve as the dispersion medium in the dispersion.

[0194] The solvent is preferably an organic solvent, more preferably an organic solvent that can be removed by vaporization when the aforementioned resin composition is heated.

[0195] The solvent content of the aforementioned resin composition is not particularly limited and can be selected arbitrarily according to the purpose.

[0196] The aforementioned resin composition can be manufactured simply by adjusting the types and amounts of its components to include the target components (constituent materials) of the aforementioned resin sheet at the target amounts. For example, the ratio of the contents of the components in the aforementioned resin composition that do not vaporize at room temperature is usually the same as the ratio of the contents of the aforementioned components in the aforementioned resin sheet.

[0197] The aforementioned resin composition can be manufactured by combining the aforementioned thermoplastic resin, the aforementioned plate-shaped filler, the aforementioned connecting filler, the aforementioned other components as needed, and the aforementioned solvent as needed.

[0198] There is no particular restriction on the order in which the ingredients are added when combining them; more than two ingredients can be added at the same time.

[0199] There are no particular limitations on the method of mixing the components during the process; any well-known method can be selected appropriately.

[0200] As long as the components do not deteriorate, there are no particular limitations on the temperature and time for adding and mixing the components, and they can be adjusted appropriately.

[0201] The aforementioned resin composition may also be a compound obtained by mixing (preferably melt mixing) the aforementioned thermoplastic resin, the aforementioned plate filler, the aforementioned connecting filler, and other aforementioned components as needed.

[0202] <<Method for Manufacturing Resin Sheets>>

[0203] The aforementioned resin sheet can be manufactured, for example, by molding the aforementioned resin composition.

[0204] The aforementioned resin composition can be molded using known methods. For example, when molding under vacuum conditions, the resin composition can be molded by vacuum heating and pressing.

[0205] The molding temperature (pressurization temperature) of the aforementioned resin composition is preferably a temperature higher than the melting point of the aforementioned thermoplastic resin. For example, it can be any one of the following: a temperature at least 15°C higher than the melting point of the aforementioned thermoplastic resin, a temperature at least 35°C higher than the melting point of the aforementioned thermoplastic resin, and a temperature at least 55°C higher than the melting point of the aforementioned thermoplastic resin. By setting the molding temperature to or above the aforementioned lower limit, the aforementioned resin sheet with higher uniformity can be obtained.

[0206] There is no particular upper limit to the aforementioned molding temperature. For example, as long as the aforementioned molding temperature is the same as or lower than the melting point of the aforementioned thermoplastic resin, overheating can be avoided.

[0207] The molding pressure of the aforementioned resin composition is not particularly limited as long as sufficient pressure is achieved, but is preferably 3 MPa or higher, for example, either 8 MPa or higher or 13 MPa or higher. By using a pressure of the aforementioned lower limit or higher, resin sheets with higher uniformity can be obtained.

[0208] There is no specific upper limit to the aforementioned pressure. For example, as long as the aforementioned pressure is below 20 MPa, excessive pressurization can be avoided.

[0209] As long as sufficient pressure can be achieved, the molding time (pressurization time) of the aforementioned resin composition is not particularly limited. For example, it can be arbitrarily set according to the pressure during molding, but is preferably 0.5 minutes or more. By setting the molding time to the aforementioned lower limit or above, resin sheets with higher uniformity can be obtained.

[0210] There is no specific upper limit to the molding time mentioned above. For example, as long as the molding time is less than 10 minutes, excessive pressure can be avoided.

[0211] The molding of the aforementioned resin composition is preferably carried out under reduced pressure, for example, more preferably under vacuum conditions such as a pressure of 0.05 MPa or less. By molding under reduced pressure in this way, the aforementioned resin sheet with higher uniformity can be obtained.

[0212] <<Resin Sheet (Solution 2)>>

[0213] The resin sheet of the second embodiment of the present invention comprises thermoplastic resin, plate-shaped filler and connecting filler, wherein the average particle size of the connecting filler is less than 2 μm.

[0214] The resin sheet of the second embodiment, because it contains the aforementioned plate-shaped filler and connecting filler, has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and its thickness direction. Furthermore, because the resin sheet of the second embodiment contains thermoplastic resin, it possesses flexibility when heated.

[0215] Except for the fact that the embedment rate R is not determined to be more than 30%, the resin sheet of the second scheme can be the same as that of the first scheme.

[0216] By covering (preferably embedding) heat-generating elements such as CPUs with a resin sheet of the second embodiment, novel heat dissipation structures can be constructed in various electronic devices, achieving a high degree of heat suppression in these devices. Furthermore, this is not limited to CPUs; heat dissipation structures can also be constructed in other devices with the same heat-generating elements as CPUs, achieving a high degree of heat suppression.

[0217] The resin sheet of the second scheme is insulating.

[0218] The resin sheet of the second embodiment may contain other components that are not among the aforementioned thermoplastic resins, plate-shaped fillers, and connecting fillers, without impairing the effects of the present invention.

[0219] The thermoplastic resin, plate-shaped filler, connecting filler, and other aforementioned components contained in the resin sheet of the second embodiment can be examples of substances that are the same as those contained in the thermoplastic resin, plate-shaped filler, connecting filler, and other aforementioned components in the resin sheet of the first embodiment.

[0220] The components contained in the resin tablet of the second embodiment have the same effect as those in the resin tablet of the first embodiment.

[0221] The resin sheet of the second embodiment, comprising thermoplastic resin, plate-shaped filler, linking filler, and the aforementioned other components, can be the same as the resin sheet of the first embodiment, comprising thermoplastic resin, plate-shaped filler, linking filler, and the aforementioned other components. More specifically, for example, as described below.

[0222] The resin sheet of the second embodiment may contain only one type of thermoplastic resin, plate-shaped filler, linking filler, and other aforementioned components, or two or more types. In the case of two or more types, the combination and ratio of these components can be arbitrarily selected according to the purpose.

[0223] For the same reasons as with the resin sheet of the first embodiment, the aforementioned thermoplastic resin contained in the resin sheet of the second embodiment is preferably an ethylene-vinyl acetate copolymer.

[0224] In the resin sheet of the second embodiment, for the same reasons as in the resin sheet of the first embodiment, the ratio of the content (parts by mass) of the aforementioned thermoplastic resin to the total mass (parts by mass) of the aforementioned resin sheet ([content (parts by mass) of thermoplastic resin in the resin sheet] / [total mass (parts by mass) of the resin sheet]×100) is preferably 20% by mass or more, preferably 45% by mass or less, for example, it can be 20 to 45% by mass, or it can be the same numerical range as in the resin sheet of the first embodiment.

[0225] For the same reasons as with the resin sheet of the first embodiment, the aforementioned plate-shaped filler contained in the resin sheet of the second embodiment is preferably composed of boron nitride (BN) or aluminum oxide (Al2O3) (i.e., boron nitride filler or aluminum oxide filler), and more preferably composed of boron nitride (i.e., boron nitride filler).

[0226] For the same reasons as the resin sheet of the first embodiment, the average particle size of the aforementioned plate-shaped filler contained in the resin sheet of the second embodiment is preferably 5 μm or more, but can be 15 μm or less, for example, it can be 5 to 15 μm, or it can be the same numerical range as the resin sheet of the first embodiment.

[0227] In the resin sheet of the second embodiment, for the same reasons as in the resin sheet of the first embodiment, the ratio of the content (volume parts) of the plate-shaped filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of the plate-shaped filler in the resin sheet] / [total volume (volume parts) of the resin sheet]×100) is preferably 10% by volume or more, preferably 35% by volume or less, for example, it can be 10 to 35% by volume, or it can be the same numerical range as in the resin sheet of the first embodiment.

[0228] For the same reasons as with the resin sheet of the first embodiment, the aforementioned connecting filler contained in the resin sheet of the second embodiment is preferably composed of magnesium hydroxide (Mg(OH)2) (i.e., magnesium hydroxide filler).

[0229] The aforementioned resin sheets containing magnesium hydroxide filler, etc., impart flame retardancy to the second type of resin sheets, for example, those that can meet UL94 standard levels V-0, V-1, or V-2.

[0230] In the resin sheet of the second embodiment, for the same reasons as in the resin sheet of the first embodiment, the ratio of the content of the binding filler to the content of the plate filler ([content of binding filler in the resin sheet (volume parts)] / [content of plate filler in the resin sheet (volume parts)]×100) is preferably 60% by volume or more, preferably 300% by volume or less, and can be 140% by volume or less. For example, it can be any one of 60 to 300% by volume and 60 to 140% by volume, or it can be the same numerical range as in the resin sheet of the first embodiment.

[0231] In the resin sheet of the second embodiment, the ratio of the content (volume parts) of the linking filler to the total volume (volume parts) of the resin sheet ([content (volume parts) of the linking filler in the resin sheet] / [total volume (volume parts) of the resin sheet]×100) preferably satisfies a numerical range that satisfies the ratio of the content of the linking filler to the content of the plate-shaped filler. For the same reasons as the resin sheet of the first embodiment, it is preferably 6% or more by volume, preferably 49% or less by volume, for example, it can be 6 to 49% by volume, or it can be the same numerical range as the resin sheet of the first embodiment.

[0232] In the resin sheet of the second embodiment, for the same reasons as in the resin sheet of the first embodiment, the ratio of the total content (parts by mass) of thermoplastic resin, plate filler and binding 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 filler in the resin sheet (parts by mass)] + [content of binding filler in the resin sheet (parts by mass)]) / [total mass (parts by mass) of the resin sheet] × 100) can be the same value range as in the resin sheet of the first embodiment, preferably 80% by mass or more and 100% by mass or less.

[0233] For the same reasons as the resin sheet in the first embodiment, the thickness of the resin sheet in the second embodiment is preferably 100 μm or more, preferably 2000 μm or less, for example, it can be 100 to 2000 μm, or it can be the same numerical range as the resin sheet in the first embodiment.

[0234] For the same reasons as the resin sheet in the first embodiment, the thermal conductivity of the resin sheet in the second embodiment in the planar direction is preferably 2 W / m·K or higher, and can be 15 W / m·K or lower, for example, 2 to 15 W / m·K, or the same range as the resin sheet in the first embodiment.

[0235] For the same reasons as the resin sheet in the first scheme, the relative permittivity of the resin sheet in the second scheme, under the condition of a frequency of 10 GHz measured by the perturbation method of the cavity resonator in the TM0m0 mode, is preferably 4 or less, but can be 1 or more, for example, 1 to 4, or the same numerical range as the resin sheet in the first scheme.

[0236] The aforementioned relative permittivity under the 10 GHz frequency condition in the second scheme is preferably a measured value at room temperature (e.g., at a temperature of 23 °C).

[0237] For the same reasons as the resin sheet in the first scheme, the relative permittivity of the resin sheet in the second scheme, measured at a frequency of 1 GHz according to the perturbation method of the cavity resonator in the TM0m0 mode, is preferably 4 or less, but can be 1 or more, for example, 1 to 4, or the same numerical range as the resin sheet in the first scheme.

[0238] In the second scheme, the aforementioned relative permittivity under the frequency of 1 GHz is preferably a measured value at room temperature (e.g., at a temperature of 23 °C).

[0239] For the same reasons as the resin sheet in the first scheme, the dielectric loss tangent of the resin sheet in the second scheme, under the condition of a frequency of 10 GHz measured by the perturbation method of the cavity resonator in the TM0m0 mode, is preferably 0.01 or less, but can be 0.001 or more, for example, 0.001 to 0.01, or the same numerical range as the resin sheet in the first scheme.

[0240] The dielectric loss tangent in the second scheme at a frequency of 10 GHz is preferably a measured value at room temperature (e.g., at a temperature of 23 °C).

[0241] For the same reasons as the resin sheet in the first scheme, the dielectric loss tangent of the resin sheet in the second scheme, under the condition of 1 GHz frequency measured by the perturbation method of the cavity resonator in the TM0m0 mode, is preferably 0.01 or less, but can be 0.001 or more, for example, 0.001 to 0.01, or the same numerical range as the resin sheet in the first scheme.

[0242] The dielectric loss tangent in the second scheme at a frequency of 1 GHz is preferably a measured value at room temperature (e.g., at a temperature of 23 °C).

[0243] In the resin sheet of the second scheme, the relative permittivity at a frequency of 10 GHz and the relative permittivity at a frequency of 1 GHz are preferably both within the above-mentioned range.

[0244] In the resin sheet of the second scheme, it is preferable that the dielectric loss tangent at a frequency of 10 GHz and the dielectric loss tangent at a frequency of 1 GHz are both within the above-mentioned value range.

[0245] 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-mentioned value range.

[0246] For the same reasons as with the resin sheet in the first embodiment, the density of the resin sheet in the second embodiment is preferably 2 g / cm³. 3 The following can be 1g / cm 3 The above, for example, can be 1-2 g / cm³. 3 It can also be the same numerical range as the resin sheet in the first scheme.

[0247] The relative permittivity, dielectric loss tangent, and density of the resin sheet in the second scheme can be adjusted, for example, by the same method as in the case of the resin sheet in the first scheme, and can be measured by the same method as in the case of the resin sheet in the first scheme.

[0248] The resin sheet of the second embodiment can be made easier to adjust in terms of its flexibility during heating by adjusting the types and contents of its components, especially the types and contents of thermoplastic resins. Thus, by adjusting the types and contents of the components in the resin sheet of the second embodiment, the resin sheet of the second embodiment can be given the same flexibility during heating as the resin sheet of the first embodiment where the embedment ratio R is determined to be 30% or more.

[0249] For the same reasons as the resin sheet in the first embodiment, the resin sheet in the second embodiment can be a resin sheet irradiated by electron beams, preferably a resin sheet irradiated by electron beams under the condition of 20 to 300 kGy of absorbed line intensity, and the accelerating voltage of electron beam irradiation is preferably 100 to 300 kV.

[0250] The resin sheet of the second embodiment can be manufactured, for example, by using a resin composition comprising the aforementioned thermoplastic resin, the aforementioned plate-shaped filler, the aforementioned connecting filler, and, if necessary, the aforementioned other components (in this specification, it is sometimes referred to as the "resin composition of the second embodiment").

[0251] Except that the types and amounts of the compounding components may differ, the resin composition of the second embodiment is the same as the resin composition used to manufacture the resin sheet of the first embodiment (the resin composition of the first embodiment).

[0252] For example, the resin composition of the second embodiment may contain a solvent, and examples of such solvents include those that are the same as those that may be contained in the resin composition of the first embodiment.

[0253] Except that the types and amounts of the compounding components may differ, the resin composition of the second embodiment can be manufactured by the same method as the resin composition of the first embodiment.

[0254] For example, except that the resin composition of the second embodiment is used instead of the resin composition of the first embodiment, the resin sheet of the second embodiment can be manufactured in the same way as the resin sheet of the first embodiment described above.

[0255] For example, for the same reasons as with the resin sheet of the first embodiment, the molding temperature (pressurization temperature) of the resin composition of the second embodiment is preferably a temperature higher than the melting point of the aforementioned thermoplastic resin. It can be a temperature that is 15°C or higher than the melting point of the aforementioned thermoplastic resin, a temperature that is the same as or lower than the melting point of the aforementioned thermoplastic resin, or a numerical range that is the same as that of the resin sheet of the first embodiment.

[0256] <<Instructions for use of the resin sheet of Scheme 1 and the resin sheet of Scheme 2>>

[0257] 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 heat-generating components such as CPUs, a novel heat dissipation structure can be constructed in various electronic devices, and heat generation in various electronic devices can be suppressed.

[0258] <Usage Method 1>

[0259] Figure 2A and Figure 2B This is a cross-sectional view schematically illustrating an example of the method of using the aforementioned resin sheet (sometimes referred to as "method 1" in this specification). Here, an example is shown where the entire area of ​​the exposed surface of the heating element is covered by the aforementioned resin sheet, i.e., where the heating element is embedded.

[0260] In addition, Figure 2A andFigure 2B In subsequent figures, the same constituent elements as those shown in the previously described figures are labeled with the same reference numerals as in the previously described figures, and their detailed descriptions are omitted.

[0261] In using method 1, firstly, as Figure 2A As shown, a laminated structure 101 is prepared, which is constructed by stacking resin sheet 1, heat diffuser 4 and housing 3 in this order in these thickness directions.

[0262] Resin sheet 1 is the resin sheet of this embodiment described above (the resin sheet of the first embodiment or the resin sheet of the second embodiment).

[0263] The housing 3 is a known housing and can be selected arbitrarily according to the purpose. Examples of materials that can be used to construct the housing 3 include resin, metal, and carbon materials.

[0264] The heat diffuser 4 is also a well-known heat diffuser, and its constituent materials include, for example, metals such as copper; carbon materials such as graphite, etc.

[0265] The circuit board 7 is not particularly limited and can be any known circuit board. A heat-generating element 5, such as a CPU, is disposed on one side surface 7a of the circuit board 7 via a connecting portion 6.

[0266] The thickness T of resin sheet 1 x Preferably within the numerical range described above.

[0267] On the other hand, the thickness T of resin sheet 1 x The height (thickness) relative to the applicable object is preferably 0.5 to 1.5 times, more preferably 0.6 to 1.3 times, for example, it can be 0.6 to 1 times. (Through T) x Above the aforementioned lower limit, it is easier to cover the applicable objects of resin sheet 1. Through T x Below the aforementioned upper limit, the thickness of the resin sheet 1 can be prevented from becoming excessive. The resin sheet 1 has high flexibility when heated; therefore, when the resin sheet 1 is pressed against the applicable object, an area is created on the resin sheet 1 that is pushed open by the applicable object, and this area helps to maintain the thickness of the resin sheet 1. Therefore, even if T... x Even if the height (thickness) of the object to which it is applied is less than 1 times, the resin sheet 1 can still be fully embedded in the object to which it is applied.

[0268] The thickness T of resin sheet 1 x Preferably, the numerical ranges described above are satisfied, and the numerical ranges based on the height of the applicable object are also satisfied.

[0269] When the height (thickness) of the object to be applied is not fixed, the height of the highest part (the thickness of the thickest part) shall be taken as the height (thickness) of the object to be applied.

[0270] Here, the applicable objects for the resin sheet 1 are, for example, the heating element 5 and the connecting part 6, when the resin sheet 1 covers the entire exposed area of ​​the heating element 5 and the entire exposed area of ​​the connecting part 6. Figure 2A The figure in the middle is marked with the symbol T. y The height is indicated by this. In contrast, for example, when the resin sheet 1 covers the entire exposed area of ​​the heating element 5 but not the connecting portion 6, the resin sheet 1 is applicable to the entire area of ​​the heating element 5. For example, when the resin sheet 1 only covers a portion of the exposed surface of the heating element 5, the resin sheet 1 is applicable to the area of ​​the heating element 5 corresponding to that portion of the exposed surface.

[0271] The laminated structure 101 has the resin sheet 1 facing the heating element 5 (in other words, the housing 3 is facing the side opposite to the heating element 5) positioned near the heating element 5. That is, one side surface 1a of the resin sheet 1 is opposite to the exposed surface 5a of the heating element 5.

[0272] Then, in method 1, the laminated structure 101 is moved in the direction of arrow P1 to press the resin sheet 1 into 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 into the resin sheet 1, or the laminated structure 101 is moved in the direction of arrow P1 while 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 into the heating element 5. Thus, as Figure 2B As shown, the heating element 5 is covered with a resin sheet 1. At this time, a portion of one side 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 opposite to the resin sheet 1. Then, other areas of one side surface 1a of the resin sheet 1 are brought into contact with or close to one side surface 7a of the circuit board 7. Thus, the entire area of ​​the exposed surface 5a of the heating element 5 (including all areas of the upper surface and side surface) is covered with the resin sheet 1, and the heating element 5 is embedded.

[0273] exist Figure 2A and Figure 2B The diagram shows a state where one heating element 5 is provided on one side surface 7a of the circuit board 7. However, the heating element provided on one side surface 7a of the circuit board 7 can be only one or more. When there are two or more heating elements provided on one side surface 7a of the circuit board 7, these two or more heating elements can be the same as each other or different from each other. That is, two or more heating elements can be all the same, all different, or only partially the same.

[0274] There are two or more heating elements disposed on one side surface 7a of the circuit board 7. When these two or more heating elements are covered by a single resin sheet 1, as described above, other areas of one side surface 1a of the resin sheet 1 are brought into contact with or close to one side surface 7a of the circuit board 7. This allows all heating elements to be easily and adequately covered by a single resin sheet 1.

[0275] When there are two or more heating elements disposed on one side surface 7a of the circuit board 7, at least a portion of the heating elements can be covered separately by two or more resin sheets 1 instead of being covered as a single unit.

[0276] Cover the heating element 5 with resin sheet 1 (in) Figure 2B When embedding the heating element 5, it is preferable to adjust the temperature of the heating element 5 to, for example, the same as the molding temperature (pressurization temperature) of the aforementioned resin composition (a temperature based on the melting point of the aforementioned thermoplastic resin). By adjusting the temperature of the heating element 5 in this way, the resin sheet 1 can more evenly cover the heating element 5, the heat dissipation of the resin sheet 1 becomes higher, and the heat dissipation efficiency of the heating element 5 becomes higher. The temperature of the heating element 5 can be adjusted, for example, using known temperature adjustment methods such as an oven.

[0277] Cover with resin sheet 1 ( Figure 2B When the heating element 5 is embedded, the pressure applied to the resin sheet 1 when pressing the resin sheet 1 into 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 into the resin sheet 1 are preferably 10 to 20 kPa. By setting the pressure above the aforementioned lower limit, the heating element 5 can be more evenly covered by the resin sheet 1. By setting the pressure below the aforementioned upper limit, excessive pressure can be avoided. The resin sheet 1 has high flexibility when heated, so even a low pressure of around 10 to 20 kPa can adequately cover the heating element 5.

[0278] With the heating element 5 covered by the resin sheet 1, the resin sheet 1 has high flexibility during heating, resulting in a high degree of adhesion between the resin sheet 1 and the heating element 5, and a high degree of adhesion between the resin sheet 1 and the connecting portion 6. More specifically, gaps can be suppressed between one side surface 1a of the resin sheet 1 and the exposed surface 5a of the heating element 5, and between one side 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, the aforementioned gaps can be eliminated (the aforementioned gaps are completely eliminated).

[0279] Thus, with the heating element 5 covered by the resin sheet 1, the heat generated in the heating element 5 is distributed along the surface direction D of the resin sheet 1. S Conduction, such as heat dissipation into the atmosphere.

[0280] Furthermore, the heat generated in the heating element 5 is distributed along the thickness direction D of the resin sheet 1. T The heat is conducted and released into the atmosphere via the heat diffuser 4. At this time, since the heating element 5 is embedded in the resin sheet 1, the distance between the heating element 5 and the heat diffuser 4 becomes closer compared to the case where it is not embedded, and the distance in the thickness direction D... T The heat dissipation is improved. Furthermore, along the thickness direction D of the resin sheet 1... T The conducted heat can sometimes be released into the atmosphere through the circuit board 7.

[0281] When the housing 3 is made of a highly thermally conductive material such as metal or carbon, along the thickness direction D of the resin sheet 1... T The conducted heat is released into the atmosphere not only through the heat diffuser 4 but also through the housing 3.

[0282] When the housing 3 is made of a material with high thermal conductivity such as metal or carbon, the heat diffuser 4 is sometimes omitted in the stacked structure 101.

[0283] As described above, the resin sheet 1 has high thermal conductivity and high heat dissipation in both its surface and thickness directions, and it also exhibits high flexibility when heated. This heat dissipation structure via the resin sheet 1 in method 1 is unprecedented in conventional heat dissipation structures.

[0284] <Usage Method 2>

[0285] Figure 3A and Figure 3B This is a cross-sectional view schematically illustrating another example (sometimes referred to as "method 2" in this specification) of the use of the aforementioned resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment). Here, an example is shown where the aforementioned resin sheet only covers a portion of the exposed surface of the heating element, i.e., the heating element is not embedded.

[0286] like Figure 3A As shown, the laminated structure 101 prepared in method 2 is the same as the laminated structure 101 prepared in method 1. Furthermore, in method 2, the resin sheet 1 is applied to the heating element 5, more specifically, to the area of ​​the heating element 5 corresponding to a portion of the exposed surface 5a, with a height T. y This is different from the case of using method 1.

[0287] Then, in method 2, such as Figure 3BAs shown, the heating element 5 is covered with resin sheet 1 in the same manner as in method 1. However, in this case, the area on one side surface 1a of resin sheet 1 that does not contact the aforementioned upper surface of the exposed surface 5a of heating element 5 does not reach the position corresponding to the contact portion between heating element 5 and connecting part 6 in the thickness direction of resin sheet 1, so that a portion below (side) of the exposed surface 5a of heating element 5 is exposed. Therefore, resin sheet 1 is not embedded in heating element 5.

[0288] With the resin sheet 1 covering the heating element 5, the resin sheet 1 has high flexibility during heating, resulting in a high degree of adhesion between the resin sheet 1 and the heating element 5, similar to the case of method 1. More specifically, gaps can be suppressed between the resin sheet 1 and the area reached by the resin sheet 1 in the thickness direction of the exposed surface 5a of the heating element 5. By adjusting the conditions when covering the heating element 5 with the resin sheet 1, the aforementioned gaps can be eliminated (the aforementioned gaps are completely eliminated).

[0289] As described above, except for the different objects to which the resin sheet 1 is applied (for example, the resin sheet 1 is used to cover only a portion of the exposed surface 5a of the heating element 5 instead of the entire area), the method of use 2 is the same as the method of use 1, and the effect of the method of use 2 is the same as the effect of the method of use 1.

[0290] <Other usage methods>

[0291] The method of using the aforementioned resin sheet (the resin sheet of the first embodiment and the resin sheet of the second embodiment) is not limited to method 1 and method 2. For example, it can be a method of use by changing, deleting or adding a part to method 1 or method 2.

[0292] For example, when a resin sheet is used to cover the heating element, one side surface of the resin sheet (the side of the circuit board, for example...) Figure 3B The region closest to the circuit board side on one side surface 1a) of the resin sheet 1 is not adjacent to the side surface of the circuit board (the surface of the resin sheet side, for example). Figure 3B When one side surface 7a) of the circuit board 7 is in contact, it can be positioned in the thickness direction of the resin sheet and at the same position as the contact portion between the heating element 5 and the connecting portion 6.

[0293] For example, on one side surface of the resin sheet (the side surface on the circuit board side, for example) Figure 3B One side surface 1a of the resin sheet 1 in the middle) and the exposed surface of the heating element (e.g., Figure 3B Between the exposed surface 5a of the heating element 5 in the middle, and one side surface of the resin sheet (the side of the circuit board, for example) Figure 3B One side surface 1a of the resin sheet 1 in the middle) and the connecting part (e.g., Figure 3BThere may be a gap between the connecting parts 6) in the middle.

[0294] As explained above, the resin sheet of this embodiment has excellent properties for covering (preferably embedding) the heating element due to its high flexibility when heated. Therefore, the heat dissipation of the resin sheet of this embodiment is extremely excellent.

[0295] In contrast, conventional heat dissipation sheets such as graphite sheets have excellent heat dissipation performance, but they lack the ability to follow the object being cooled and their adhesion to the object is insufficient. Therefore, they are not suitable as heat dissipation structures that are set separately on the heat source. Moreover, heat dissipation sheets such as graphite sheets are also conductive sheets. Due to their conductivity (lack of insulation), they cannot be used in the vicinity of the antenna.

[0296] For example, thermal interface materials (TIMs) have good adhesion to the object being cooled and good insulation, but they are not good at heat dissipation and following the object being cooled.

[0297] For example, heat dissipation materials that are liquid at room temperature are also known, but the use of liquid heat dissipation materials is limited to sealed spaces, and the filling process is complicated and the repairability is poor.

[0298] The resin sheet of this embodiment can solve all such previous problems.

[0299] Example

[0300] The present invention will be further described in detail below through specific embodiments. However, the present invention is not limited to the embodiments shown below.

[0301] The following shows the raw materials and ingredients used in the embodiments and comparative examples.

[0302] [Thermoplastic resin]

[0303] Thermoplastic resin (a1): Ethylene-vinyl acetate copolymer (EVA) (EVAFLEX EV150 manufactured by Dow-Mitsui Polychemicals, Inc., with a melting point of approximately 60°C, a melt flow rate (MFR) of 30 g / 10 min, and a density of 0.96 g / cm³). 3 Vinyl acetate content 33% (by mass).

[0304] The aforementioned MFR of EVA is the measured value when a load of 2.16 kg is applied at a temperature of 190°C in accordance with JIS K7210:1999.

[0305] [Plate packing]

[0306] Plate-shaped packing (b1): Plate-shaped boron nitride packing ("K03" manufactured by Tokuyama Corporation, with an average particle size of 9 μm and a density of 2.3 g / cm³). 3 Thermal conductivity 60 W / m·K, aspect ratio 30, relative permittivity 4).

[0307] [Connecting packing]

[0308] Connecting filler (c1): Magnesium hydroxide filler with surface treatment of higher fatty acids (KISUMA 5B manufactured by Kyowa Chemical Industry Co., Ltd., with a magnesium hydroxide content of 95% by mass or more, a higher fatty acid content of 5% by mass or less, an average particle size of 0.83 μm, and a thermal conductivity of 8 W / m·K).

[0309] Connecting filler (c2): Magnesium hydroxide filler with surface treatment of organosilicon compound (silane coupling agent) (KISUMA 5P manufactured by Kyowa Chemical Industry Co., Ltd., with a magnesium hydroxide content of ≥95% by mass, an organosilicon compound content of ≤5% by mass, an average particle size of 0.72μm, and a thermal conductivity of 8W / m·K).

[0310] Connecting filler (c3): Magnesium hydroxide filler with surface treatment of organosilicon compound (silane coupling agent) (KISUMA (registered trademark) 5L manufactured by Kyowa Chemical Industry Co., Ltd., with a magnesium hydroxide content of ≥95% by mass, an organosilicon compound content of ≤5% by mass, an average particle size of 0.72μm, and a thermal conductivity of 8W / m·K).

[0311] Connecting filler (c4): Magnesium hydroxide filler (KISUMA 5 manufactured by Kyowa Chemical Industry Co., Ltd., with an average particle size of 0.83 μm and a thermal conductivity of 8 W / m·K).

[0312] Connecting filler (c5): Magnesium hydroxide filler (KISUMA 8 manufactured by Kyowa Chemical Industry Co., Ltd., with an average particle size of 1.38 μm and a thermal conductivity of 8 W / m·K).

[0313] [Other fillers]

[0314] Other fillers (d1): Card-shaped alumina filler (DIC company "AC75", average particle size 70μm, density 3.97g / cm³). 3 Thermal conductivity 20 W / m·K.

[0315] Other fillers (d2): Polyhedral alumina filler (DIC company's "AH40-S", average particle size 32μm, density 3.97g / cm³).3 Thermal conductivity 20 W / m·K.

[0316] [Example 1]

[0317] <<Manufacturing of Resin Sheets>>

[0318] A granular resin composition was prepared by melt-blending thermoplastic resin (a1) (500g), plate filler (b1) (600g), linker filler (c1) (250g), linker filler (c2) (100g) and linker filler (c3) (100g) using a twin-screw extruder.

[0319] Furthermore, the aforementioned resin composition, obtained by clamping it with a pair of hot plates, was molded by vacuum heating and pressing at 120°C for 1 minute under vacuum conditions of 0.02 MPa or less, while being heated at 15 MPa, and a single-layer resin sheet (700 μm thick) was obtained.

[0320] <<Evaluation of Resin Sheets>>

[0321] <Calculation of Embedding Rate R>

[0322] The three resin sheets (700 μm thick) obtained by the above method were stacked in the thickness direction and cut into 3.5 cm × 3.5 cm sizes, thereby producing a test piece with a thickness T0 of 2100 μm and a planar shape of quadrilateral.

[0323] Then, the obtained test piece was placed on a flat surface, and a cylindrical ceramic press-fit material with a diameter of 16 mm and a height of 14 mm was placed near the center of the exposed, upward-facing surface of the test piece. At this point, one side of the press-fit material, rather than its curved surface, was in contact with the exposed surface of the test piece. Furthermore, a weight was placed on the entire surface of the other side of the press-fit material (the exposed, upward-facing surface that is not in contact with the exposed surface of the test piece). Thus, by sequentially stacking the test piece, the press-fit material, and the weight, a pressure of 12 kPa was applied to the test piece in the thickness direction. The stack was then immediately transferred to an environment at 100°C and left to stand for 10 minutes. Thus, a pressure of 12 kPa was applied to the test piece in the thickness direction for 10 minutes at 100°C.

[0324] Then, immediately after 10 minutes, the thickness T1 of the test piece at the pressure-applied location in the laminate was measured. The embedment rate R of the test piece (resin sheet) was then calculated using the aforementioned formula. The results are shown in Table 1.

[0325] <Confirmation of the heat dissipation properties of the resin sheet (1)>

[0326] The resin sheet obtained above (700μm thick) was cut into 10cm×10cm pieces.

[0327] On the circuit surface of the circuit board, four resistors are arranged in a row at approximately equal intervals. Reference numerals (1-1) to (1-4) are used to label these four resistors from one end of the row to the other. Furthermore, in a direction orthogonal to the direction of the row, on the same side as these four resistors (i.e., resistors (1-1), (1-2), (1-3), and (1-4)), one additional resistor is arranged at approximately equal intervals for each of these four resistors. Reference numerals (2-1) to (2-4) are used to label these four additionally arranged resistors from one end of the row to the other. Resistor (2-1) is adjacent to resistor (1-1) but not to resistor (1-4); resistor (2-2) is adjacent to resistor (1-2) but not to resistor (1-3); resistor (2-3) is adjacent to resistor (1-3) but not to resistor (1-2); and resistor (2-4) is adjacent to resistor (1-4) but not to resistor (1-1). Thus, a total of eight resistors are arranged on the circuit surface of the circuit board, divided into two columns of four, with adjacent resistors spaced approximately evenly in two orthogonal directions. The height of these eight resistors (i.e., the distance between the upper surface of the resistor (the side opposite to the circuit board side) and the circuit surface of the circuit board) is approximately 4 mm. Figure 4 The diagram shows a top view schematically illustrating the arrangement of resistors on the circuit board at this point.

[0328] Then, in one column of four resistors, a thin-wire thermocouple is placed for each of the two resistors at both ends (resistor (1-1) and resistor (1-4)). Furthermore, in another column of four resistors, a thin-wire thermocouple is placed for the second resistor from one end (resistor (2-2)). Then, a thin-wire thermocouple is placed in the portion of the circuit surface of the circuit board that is in the middle of these two columns and also approximately at the center of these two columns in the column direction (approximately the center of the circuit surface of the circuit board) where no resistors are currently placed. That is, one thermocouple is placed for each of three of the eight resistors on the circuit surface, and one thermocouple is placed on the circuit surface (not on the resistor itself). The placement of the thermocouples at this point is summarized as follows: Figure 4 .

[0329] Then, for each of the eight resistors on the circuit board, a sheet of thermal interface material (TIM, "Thermo-TranzH2" manufactured by Wide Work Company, 500 μm thick) was laminated across the entire surface of the side of the resistor opposite to the circuit board side. This was done to avoid height errors caused by the fact that the heights of the eight resistors were not strictly identical, which could affect the evaluation results. Therefore, the thermocouples on the resistors were positioned between the resistors and the thermal interface material (TIM) sheets. Furthermore, a resin sheet (700 μm thick) obtained above was used to completely cover the entire surface of the side of these thermal interface material sheets opposite to the resistor side. Moreover, a polycarbonate substrate (2000 μm thick) was placed on the entire surface of the side of the covered resin sheet opposite to the thermal interface material sheet side. Thus, a test circuit board for evaluating the heat dissipation performance of the resin sheet was fabricated.

[0330] A thermal imager was installed on the upper part of the polycarbonate substrate side of the experimental circuit board obtained above.

[0331] Then, the voltage of all eight resistors in the test circuit board was adjusted to consume 10W, and a voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate substrate was measured using a thermal imager. The image data acquired at this time is shown below. Figure 5 Furthermore, the thermocouple-based detection temperatures of resistors (1-1), (1-4), (2-2), and the circuit surface are shown in Table 1.

[0332] <Determination of thermal conductivity of resin sheet in the planar direction>

[0333] The thermal conductivity in the planar direction of the resin sheet obtained above was measured using a hot plate thermal property measuring apparatus ("TPS 500 S" manufactured by Kyoto Electronics Industry Co., Ltd.). Two resin sheets were sandwiched 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.

[0334] <Determination of the relative permittivity and dielectric loss tangent of resin sheets>

[0335] At room temperature, test pieces of a specific size were cut from the resin sheet obtained above. For these test pieces, the relative permittivity and dielectric loss tangent at frequencies of 1 GHz and 10 GHz were determined using the TM0m0 mode cavity resonator perturbation method. The results are shown in Table 1.

[0336] <Determination of the density of resin sheets>

[0337] The density of the resin sheets obtained above was determined in accordance with JIS K7112:1999. The results are shown in Table 1.

[0338] <<Manufacturing and Evaluation of Resin Sheets>>

[0339] [Comparative Example 1]

[0340] A granular resin composition was prepared by melt-blending thermoplastic resin (a1) (500g), other fillers (d1) (1000g), linker filler (c4) (300g) and linker filler (c5) (300g) using a twin-screw extruder.

[0341] Then, except that a granular resin composition was used, resin sheets (700 μm thick) were manufactured and evaluated using the same method as in Example 1. The results are shown in Table 1 and Figure 6 . Figure 6 The image data was obtained when the heat dissipation performance of the resin sheet was confirmed in this comparative example.

[0342] [Comparative Example 2]

[0343] A granular resin composition was prepared by melt-blending thermoplastic resin (a1) (500g), other fillers (d2) (1000g), linker filler (c4) (300g) and linker filler (c5) (300g) using a twin-screw extruder.

[0344] Then, except that a granular resin composition was used, resin sheets (700 μm thick) were manufactured and evaluated using the same method as in Example 1. The results are shown in Table 1 and Figure 7 . Figure 7 The image data was obtained when the heat dissipation performance of the resin sheet was confirmed in this comparative example.

[0345] <<Evaluation of the test resin sheets>>

[0346] <Confirmation of the heat dissipation performance of the test resin sheet>

[0347] [Experimental Example 1]

[0348] As the test resin sheet, a commercially available thermally conductive sheet (500 μm thick) with rubber as its main component and a thermal conductivity of 3 W / m·K in its surface direction was prepared.

[0349] Using the same method as in "confirmation of the heat dissipation of the resin sheet" in Example 1, eight resistors and four thermocouples were arranged on the circuit surface of the circuit board.

[0350] Then, for each of the eight resistors on the circuit board, with thermocouples in place, a sheet of thermal interface material (TIM, "Thermo-TranzH2" manufactured by Wide Work Company, 500 μm thick) was laminated across the entire surface of the side of the resistor opposite to the circuit board side. This positioned the thermocouple between the resistor and the TIM sheet. Furthermore, a single 500 μm thick test resin sheet completely covered the entire surface of the TIM sheet opposite to the resistor side. Finally, a polycarbonate substrate (2000 μm thick) was placed on the entire surface of the test resin sheet opposite to the TIM sheet. This created a test circuit board for evaluating the heat dissipation performance of the test resin sheet.

[0351] Hereinafter, 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 thermal imager. The image data acquired at this time is shown below. Figure 8 Furthermore, the thermocouple-based temperature readings on the resistors and circuit surfaces are shown in Table 1.

[0352] In Table 1, "content of plate filler (volume %)" refers to the ratio of the content (volume parts) of plate filler in the resin sheet to the total volume (volume parts) of the resin sheet.

[0353] Similarly, "content of linking filler (volume %)" refers to the ratio of the content (volume parts) of linking filler in the resin sheet to the total volume (volume parts) of the resin sheet.

[0354] "The ratio of the content of the linking filler to the content of the plate filler (volume %)" refers to the ratio of the content (volume parts) of the linking filler in the resin sheet to the content (volume parts) of the plate filler.

[0355] The same information is also found in the tables following Table 1.

[0356] [Table 1]

[0357] The results above show that the embedding rate R in Example 1 is as high as 43.8%, and the resin sheet has high flexibility when heated.

[0358] Then, as Figure 5As shown, the area on the surface of the polycarbonate substrate where the four resistors in the same column are located carries heat of approximately 65-85°C across these resistors, and the same applies to the area where two columns are located. Furthermore, the area between these two columns also carries heat of approximately 60-65°C. This indicates that the heat generated from the four resistors in the same column is dissipated not only along the length of the column but also along its width, demonstrating that the resin sheet has high heat dissipation in its surface direction. On the other hand, as shown in Table 1, when comparing the thermocouple-based detection temperatures between identical resistors and between the circuit surfaces of the circuit board in Example 1 and Test Example 1, the detection temperature in Example 1 is lower than that in Test Example 1. This indicates that, compared to the test resin sheet (commercially available thermally conductive sheet) in Test Example 1, the resin sheet in Example 1 has high heat dissipation not only in its surface direction but also in its thickness direction. In the above evaluation, the heat dissipation performance of the resin sheet for the heating element (resistor) was simply confirmed without embedding the resin sheet in the heating element. However, it is speculated that the resin sheet of Example 1, by more extensively covering (preferably embedding) the heating element, also exhibits high heat dissipation performance. Thus, it was confirmed that the resin sheet of Example 1 has high flexibility when heated, high heat dissipation performance in both its surface and thickness directions, and can form a novel heat dissipation structure.

[0359] The resin sheet of Example 1 comprises thermoplastic resin, plate-shaped filler, and linker filler. Furthermore, in the sheet of Example 1, the ratio of linker filler content to plate-shaped filler content is 72.0% by volume.

[0360] The relative permittivity of the resin sheet in Example 1 is less than 4 in both 1 GHz and 10 GHz frequencies.

[0361] The dielectric loss tangent of the resin sheet in Example 1 is less than 0.01 in both 1 GHz and 10 GHz.

[0362] The density of the resin sheet in Example 1 is less than 2 g / cm³. 3 .

[0363] In contrast, in Comparative Example 1, the embedment rate R was as low as 11.0%, the resin sheet had low flexibility when heated, and the resin sheet failed to cover (preferably embed) the heating element more extensively.

[0364] Moreover, such as Figure 6As shown, the area on the surface of the polycarbonate substrate where the four resistors in the same column are located carries heat of approximately 65-85°C across these resistors. This is also true in the area where two columns are located, but this heated area is narrower than in Example 1. Furthermore, the area between these two columns does not carry high heat. This indicates that the heat generated from the four resistors in the same column is dissipated through the resin sheet along the length of the column, but its heat dissipation efficiency is lower than that of Example 1. Moreover, the heat dissipation efficiency in the width direction of the column is also lower than that of Example 1, and it indicates that the heat dissipation efficiency of the resin sheet in Comparative Example 1 in its surface direction is lower than that of the resin sheet in Example 1. On the other hand, as shown in Table 1, in Comparative Example 1 and Test Example 1, when comparing the thermocouple-based detection temperatures between the same resistors, the detection temperature of Comparative Example 1 is higher than that of Test Example 1, and the heat dissipation efficiency of the resin sheet in Comparative Example 1 is lower than that of the test resin sheet (commercially available thermally conductive sheet) in Test Example 1. Thus, the resin sheet of Comparative Example 1 has low flexibility when heated and low heat dissipation efficiency in both its surface and thickness directions.

[0365] The resin sheet of Comparative Example 1 contains a binding filler but not a plate-shaped filler; instead, it contains other fillers (d1). The other fillers (d1) are card-shaped and plate-shaped alumina aggregated into spherical aggregates.

[0366] In Comparative Example 2, the embedment rate R was as high as 49.5%, and the resin sheet exhibited high flexibility when heated.

[0367] like Figure 7 As shown, the area on the surface of the polycarbonate substrate where the four resistors in the same row exist carries heat of approximately 65-85°C across these resistors, and the same applies to the area where two rows exist. However, in Comparative Example 2, this heated area is narrower than in Example 1. Then, similar to Comparative Example 1, the area between these two rows does not carry high heat. These results indicate that the resin sheet of Comparative Example 2, like the resin sheet of Comparative Example 1, has lower heat dissipation in its surface direction than the resin sheet of Example 1. On the other hand, as shown in Table 1, in Comparative Example 2 and Test Example 1, when comparing the thermocouple-based detection temperatures between the same resistors, similar to Comparative Example 1, the detection temperatures of Comparative Example 2 are higher than those of Test Example 1, and the heat dissipation of the resin sheet of Comparative Example 2 is lower than that of the test resin sheet (commercially available thermally conductive sheet) of Test Example 1. Then, in Comparative Example 2, the aforementioned detection temperatures are higher than those of Comparative Example 1, and the heat dissipation of the resin sheet of Comparative Example 2 is lower than that of the resin sheet of Comparative Example 1. Thus, the resin sheet of Comparative Example 2 has low heat dissipation in both the surface direction and the thickness direction.

[0368] The resin sheet of Comparative Example 2 contains a binding filler but not a plate-shaped filler; instead, it contains other fillers (d2). The other filler (d2) is a polyhedral alumina filler.

[0369] The relative permittivity of the resin sheets in Comparative Examples 1 and 2 exceeded 4 in both the 1 GHz and 10 GHz frequencies.

[0370] The density of the resin sheets in Comparative Examples 1 and 2 exceeded 2 g / cm³. 3 .

[0371] The test resin sheet (commercially available thermally conductive sheet) used in Test Example 1 did not have the flexibility to be heated and failed to cover or embed the heating element more extensively.

[0372] In Experiment 1, such as Figure 8 As shown, the area on the surface of the polycarbonate substrate where the four resistors in the same row exist carries heat of approximately 60-80°C across these resistors, and the same applies to the area where two rows exist. However, in Test Example 1, this heated area is narrower than in Example 1. Furthermore, the area between these two rows does not carry high heat. These results indicate that the heat dissipation of the resin sheet in Test Example 1 is lower than that of the resin sheet in Example 1 in its surface direction. As described above, in Test Example 1 and Example 1, when comparing the thermocouple-based detection temperatures between the same resistors and between the circuit surfaces of the circuit board, the detection temperature of Test Example 1 is higher than that of Example 1, and the heat dissipation of the test resin sheet in Test Example 1 is lower than that of the resin sheet in Example 1.

[0373] [Example 2]

[0374] <<Manufacturing of Resin Sheets>>

[0375] Except for changing the amount of granular resin composition used, a single-layer resin sheet (1500 μm thick) was manufactured using the same method as in Example 1. That is, the only difference between the resin sheet of this example and the resin sheet of Example 1 is its thickness.

[0376] <<Evaluation of Resin Sheets>>

[0377] <Confirmation of the heat dissipation properties of the resin sheet (2)>

[0378] The resin sheet obtained above (1500μm thick) is cut into 10cm×10cm pieces.

[0379] As a circuit board equipped with resistors and thermocouples, a circuit board identical to that in Example 1 was prepared. Figure 4 The circuit board shown.

[0380] Then, for all eight resistors on the circuit board, with thermocouples in place, a resin sheet (1500 μm thick) obtained above was used to completely cover and press the entire surface of the resistor's side opposite to the circuit board side. This positioned the thermocouple between the resistor and the resin sheet. Furthermore, a polycarbonate substrate (2000 μm thick) was placed on the entire surface of the resin sheet's side opposite to the resistor side. This created a test circuit board for evaluating the heat dissipation performance of the resin sheet.

[0381] In the circuit board used for this test, the distance between the resistor-side face of the polycarbonate substrate and the polycarbonate substrate-side face of the resistor was confirmed for every 8 resistors, and the result was approximately 400 μm. Therefore, the embedment distance of the resin sheet covering the area of ​​the resistor is approximately 1100 μm (=1500 μm - 400 μm).

[0382] A thermal imager was installed on the upper part of the polycarbonate substrate side of the experimental circuit board obtained above.

[0383] Then, the voltage of all eight resistors in the test circuit board was adjusted to consume 10W, and a voltage was applied to the test circuit board. Under these conditions, the surface temperature of the polycarbonate substrate was measured using a thermal imager. The thermocouple-based detection temperatures of resistors (1-1), (1-4), (2-2), and the circuit surface at this time are shown in Table 2.

[0384] <<Evaluation of Resin Sheets>>

[0385] <Confirmation of the heat dissipation properties of the resin sheet (2)>

[0386] [Example 1]

[0387] The heat dissipation performance of the resin sheet (700 μm thick) from Example 1 was confirmed using the same method as in Example 2. The thermocouple-based temperature readings at this time are shown in Table 2.

[0388] In the test circuit board used in this embodiment, the distance between the resistor-side face of the polycarbonate substrate and the polycarbonate substrate-side face of the resistor was confirmed for every 8 resistors, and the result was approximately 400 μm. Therefore, the embedment distance of the resin sheet covering the area of ​​the resistor is approximately 300 μm (= 700 μm - 400 μm).

[0389] In this embodiment, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) of the polycarbonate substrate is set to be the same as in Embodiment 2.

[0390] <<Confirmation of the temperature of the resistor without resin sheet>>

[0391] [Experimental Example 2]

[0392] Except for the absence of a resin sheet, the experiment was conducted in the same manner as in Example 2, confirming the thermocouple-based detection temperature. The results are shown in Table 2.

[0393] <<Confirmation of the heat dissipation performance of the thermal interface material sheet>>

[0394] [Experimental Example 3]

[0395] Except that a thermal interface material (TIM) sheet (1500 μm thick) was used instead of the resin sheet used in Example 1, the heat dissipation performance of the TIM sheet was confirmed using the same method as in Example 2. In this example, for all eight resistors on the circuit surface, the entire surface of the side of the resistor opposite to the circuit board side was covered by a single TIM sheet via thermocouples when thermocouples were configured. In this example, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) of the polycarbonate substrate was set to the same as in Example 2. The thermocouple-based detection temperatures at this time are shown in Table 2. In this example, the thermocouples on the resistors were positioned between the resistors and the TIM sheet. The results are shown in Table 2.

[0396] [Table 2]

[0397] The results above show that, in Examples 1-2 and Test Example 2, when comparing the thermocouple-based detection temperatures between identical resistors and circuit surfaces of the circuit board, the detection temperatures in Examples 1-2 were significantly lower than those in Test Example 2. This is because no heat dissipation structure was provided in Test Example 2.

[0398] Furthermore, in Examples 1-2 and Test Example 3, when comparing the thermocouple-based detection temperatures between identical resistors and between the circuit surfaces of the circuit board, the detection temperatures of Examples 1-2 were lower than those of Test Example 3. This indicates that, compared to the thermal interface material sheet of Test Example 3, the resin sheets of Examples 1-2 have higher heat dissipation properties not only in their surface direction but also in their thickness direction. The embedding properties of the thermal interface material sheet of Test Example 3 are worse than those of the resin sheets of Examples 1-2.

[0399] In the above evaluation, the heat dissipation performance of the resin sheet for the heating element (resistor) was simply confirmed without embedding the resin sheet in the heating element. However, it is speculated that the resin sheet of Example 2, like the resin sheet of Example 1, also exhibits high heat dissipation performance by more extensively covering (preferably embedding) the heating element. Thus, it was confirmed that the resin sheet of Example 2 has high flexibility when heated, high heat dissipation performance in both its surface direction and thickness direction, and can form a novel heat dissipation structure.

[0400] Furthermore, in both Embodiment 1 and Embodiment 2, when comparing the thermocouple-based detection temperatures between the same resistors and the circuit surfaces of the circuit board, the detection temperature in Embodiment 2 is lower than that in Embodiment 1. This is because, in Embodiment 2, the embedding distance of the resin sheet is longer than that in Embodiment 1, thus resulting in higher heat dissipation efficiency based on the resin sheet.

[0401] [Example 3]

[0402] <<Manufacturing of Resin Sheets>>

[0403] Except for changing the content of the components in the resin sheet as shown in Table 3 and changing the amount of the granular resin composition used, a single-layer resin sheet (1541 μm thick) was manufactured in the same manner as in Example 1.

[0404] <<Evaluation of Resin Sheets>>

[0405] <Calculation of Embedding Rate R>

[0406] The embedment rate R was calculated for the resin sheet obtained above using the same method as in Example 1. The results are shown in Table 3.

[0407] <Confirmation of the heat dissipation properties of the resin sheet (3)>

[0408] The resin sheet obtained above (1500μm thick) is cut into 5cm×5cm pieces.

[0409] A resistor is disposed on the circuit surface of the circuit board. The height of the resistor (i.e., the distance between the upper surface of the resistor (the side opposite to the circuit board side) and the circuit surface of the circuit board) is 1.2 mm.

[0410] Then, a thin-wire thermocouple was placed on the resistor. Furthermore, a thin-wire thermocouple was placed on the side of the circuit board opposite to the circuit surface (back side) at the location directly below the resistor.

[0411] Then, a thermocouple is used to cover and press the entire surface of the resistor on the circuit surface, on the side opposite to the circuit board side, onto the resin sheet (1500 μm thick) obtained above. This places the thermocouple on the resistor between the resistor and the resin sheet. Furthermore, a polycarbonate substrate (2000 μm thick) is placed on the entire surface of the resin sheet on the side opposite to the resistor side. This creates a test circuit board for evaluating the heat dissipation performance of the resin sheet.

[0412] In this experimental circuit board, the distance between the resistor-side surface of the polycarbonate substrate and the polycarbonate substrate-side surface of the resistor was confirmed to be approximately 400 μm. In this experimental circuit board, the area of ​​the resin sheet on the circuit board-side surface that does not contact the resistor is in contact with the circuit board (more specifically, the circuit surface), and the resistor is completely embedded in the resin sheet.

[0413] A thermal imager was installed on the upper part of the polycarbonate substrate side of the experimental circuit board obtained above.

[0414] Then, the voltage was adjusted so that the power consumption of the resistor 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 thermal imager. The thermocouple-based temperature measurements at this time are shown in Table 3.

[0415] <Determination of thermal conductivity, relative permittivity, dielectric loss tangent, and density of resin sheets in the planar direction>

[0416] 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.

[0417] [Example 4]

[0418] <<Manufacturing of Resin Sheets>>

[0419] Except for changing the content of the components in the resin sheet as shown in Table 3 and changing the amount of granular resin composition used, a single-layer resin sheet (1550 μm thick) was manufactured in the same manner as in Example 1.

[0420] <<Evaluation of Resin Sheets>>

[0421] <Calculation of Embedding Rate R>

[0422] The embedment rate R was calculated for the resin sheet obtained above using the same method as in Example 1. The results are shown in Table 3.

[0423] <Confirmation of the heat dissipation properties of the resin sheet (3)>

[0424] The heat dissipation performance of the resin sheet obtained above was confirmed using the same method as in Example 3. The thermocouple-based temperature readings at this time are shown in Table 3.

[0425] 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 confirmed to be approximately 400 μm. In this test circuit board, similar to the case in Example 3, the area of ​​the resin sheet on the circuit board-side surface that does not contact the resistor is in contact with the circuit board (more specifically, the circuit surface), and the resistor is completely embedded in the resin sheet.

[0426] <Determination of thermal conductivity, relative permittivity, dielectric loss tangent, and density of resin sheets in the planar direction>

[0427] 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.

[0428] <<Confirmation of the temperature of the resistor without resin sheet>>

[0429] [Experimental Example 4]

[0430] Except for the absence of a resin sheet, the experiment was conducted in the same manner as in Example 3, confirming the thermocouple-based temperature detection. The results are shown in Table 3.

[0431] <<Confirmation of the heat dissipation performance of the thermal interface material sheet>>

[0432] [Experimental Example 5]

[0433] As a circuit board equipped with resistors and thermocouples, the same circuit board as in Example 3 was prepared.

[0434] Then, for the resistor on the circuit surface, a thermal interface material (TIM) sheet, identical to the one used in Test Example 1, was used to cover and press the entire surface of the resistor's side opposite to the circuit board side, via a thermocouple. That is, in this test example, unlike in Examples 3 and 4, a thermal interface material sheet (1500 μm thick) was used instead of a resin sheet. Thus, the thermocouple on the resistor was positioned between the resistor and the thermal interface material sheet. Furthermore, a polycarbonate substrate (2000 μm thick) was placed on the entire surface of the covered thermal interface material sheet on the side opposite to the resistor side. Thus, a test circuit board for evaluating the heat dissipation performance of the thermal interface material sheet was fabricated.

[0435] In this test example, the distance between the circuit surface of the test circuit board and the resistor side (circuit surface side) of the polycarbonate substrate was set to the same as in Example 3.

[0436] A thermal imager was installed on the upper part of the polycarbonate substrate side of the experimental circuit board obtained above.

[0437] Then, the voltage was adjusted so that the power consumption of the resistor 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 thermal imager. The thermocouple-based temperature measurements at this time are shown in Table 3.

[0438] [Table 3]

[0439] The results above show that, in Examples 3-4 and Test Example 4, when comparing the thermocouple-based detection temperatures between the resistors and the back sides of the circuit board, the detection temperatures in Examples 3-4 were significantly lower than those in Test Example 4. This is because no heat dissipation structure was provided in Test Example 4.

[0440] Furthermore, in Examples 3-4 and Test Example 5, when comparing the thermocouple-based detection temperatures between the resistors and the back sides of the circuit board, the detection temperatures in Examples 3-4 were lower than those in Test Example 5. This indicates that the resin sheets of Examples 3-4 have higher heat dissipation properties not only in their surface direction but also in their thickness direction, compared to the thermal interface material sheet of Test Example 5. The embedding properties of the thermal interface material sheet of Test Example 5 are worse than those of the resin sheets of Examples 3-4.

[0441] Thus, it was confirmed that the resin sheets of Examples 3-4 have high flexibility when heated, high heat dissipation in both the surface and thickness directions, and can form a novel heat dissipation structure.

[0442] Furthermore, in Examples 3 and 4, when comparing the thermocouple-based detection temperatures between the resistors and the back sides of the circuit board, the detection temperature in Example 4 was lower than that in Example 3. This is due to the difference in the resin sheet composition, as the heat dissipation effect of the resin sheet in Example 4 is higher than that in Example 3, consistent with the results of the thermal conductivity of these resin sheets in the planar direction.

[0443] The resin sheets of Examples 3 and 4 comprise thermoplastic resin, plate-shaped filler, and linker filler. Furthermore, in the sheets of Examples 3 and 4, the ratio of linker filler content to plate-shaped filler content is 99.1 to 296.6% by volume.

[0444] The resin sheet of Example 3 meets the UL94 standard level V-2 (1.5 mmt), and the resin sheet of Example 4 meets the UL94 standard level V-0 (1.5 mmt).

[0445] The relative permittivity of the resin sheets in Examples 3 and 4 is 4 or less in either the 1 GHz or 10 GHz frequency case.

[0446] The dielectric loss tangent of the resin sheets in Examples 3 and 4 is less than 0.01 in both 1 GHz and 10 GHz cases.

[0447] The density of the resin sheets in Examples 3 and 4 is less than 2 g / cm³. 3 .

[0448] Industrial applicability

[0449] In electronic devices equipped with a CPU, the present invention can be used to construct a novel heat dissipation structure, but it is not limited to CPUs. It can also be used to construct a heat dissipation structure in other devices that have the same heat-generating element as a CPU.

[0450] Explanation of reference numerals in the attached figures

[0451] 1: Resin sheet.

[0452] 3: Box.

[0453] 4: Thermal diffuser.

[0454] 5: Heating element.

[0455] 6: Connecting part.

[0456] 7: Circuit board.

[0457] 8: Heavy objects.

[0458] 9: Press in the material.

[0459] 10: Test piece.

[0460] D S : The orientation of the resin sheet's surface.

[0461] D T : The thickness direction of the resin sheet.

[0462] T0: Thickness of the test piece.

[0463] T1: The thickness of the test piece at the pressurized part after heating and pressurization.

Claims

1. A resin sheet, wherein the resin sheet comprises a thermoplastic resin, a platy filler, and a bonding filler, the average particle diameter of the bonding filler is 2 μm or less.

2. A resin sheet, wherein the resin sheet comprises a thermoplastic resin, a platy filler, and a bonding filler, the average particle diameter of the bonding filler is 2 μm or less, a test piece having a thickness of TO using one resin sheet or a laminate of two or more resin sheets, is subjected to a pressure of 12 kPa for 10 minutes in the thickness direction of the test piece in an environment of 100°C, and the embedding rate R calculated from the following equation: R = (TO - Tl) / TO x 100 is 30% or more at the portion to which the pressure is applied.

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

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

5. The resin sheet according to claim 1 or 3, wherein the platy filler is composed of boron nitride or alumina.

6. The resin sheet according to claim 1 or 3, wherein the bonding filler is composed 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 in the resin sheet, the ratio of the content of the bonding filler to the content of the platy filler is 60 to 140 vol%.

9. The resin sheet according to claim 1 or 3, wherein the average particle diameter of the platy filler is 5 μm or more.

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

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

12. The resin sheet according to claim 2 or 10, wherein the platy filler is composed of boron nitride or alumina.

13. The resin sheet according to claim 2 or 10, wherein the bonding filler is composed 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 in the resin sheet, the ratio of the content of the bonding filler to the content of the platy filler is 60 to 140 vol%.

16. The resin sheet according to claim 2 or 10, wherein the average particle diameter of the platy filler is 5 μm or more.

Images