Patent Application
20240387901
The present disclosure relates to a heat conductive material, a method for producing the heat conductive material, and a battery module.
A technique of radiating heat generated by a heat generating material using a heat radiating material has been known. For example, in electronic equipment such as a computer, a heat radiating element such as a heat sink is used for radiating heat generated by a heat generating element such as a semiconductor element. For the purpose of improving heat conduction efficiency from the heat generating element to the heat radiating element, a heat conductive material may be disposed between the heat generating element and the heat radiating element.
Patent Literature 1 discloses a heat conductive compact configured by magnetic field orientation of boron nitride powder in constant direction in a polymer. Also, Patent Literature 2 discloses a heat conductive resin compact comprising, as a heat conductive filler, a heat conductive particle with high magnetic field responsiveness and a heat conductive particle with low magnetic field responsiveness, wherein the heat conductive particle with high magnetic field responsiveness is oriented in a thickness direction of the compact. Also, Patent Literature 3 discloses a sheet shape heat radiating material comprising: a heat conductive filler including an agglomerated hexagonal boron nitride powder having a specified orientation property index, and an aluminum oxide powder; and a silicone resin.
Since electronic equipment in recent years has high heat generation density and is often used under high voltage, it is important to secure the heat radiation properties and insulation properties. Also, for example, batteries also generate heat during charge and discharge, and are used under high voltage, and thus it is important to secure the heat radiation properties and insulation properties. A material with high conductivity (low insulation properties) such as a metal is often used as the heat radiating element, and thus the heat conductive material disposed between the heat generating element and the heat radiating element is required to have excellent insulation properties in addition to excellent heat conductivity. Details will be described later, but when aiming to improve the heat conductivity, the insulation properties may be insufficient, and it is difficult to achieve both of the heat conductivity and the insulation properties.
The present disclosure has been made in view of the above circumstances, and a main object thereof is to provide a heat conductive material that achieves both heat conductivity and insulation properties.
A heat conductive material comprising a matrix resin and a filler, wherein
The heat conductive material according to [1], wherein a dielectric breakdown voltage of the heat conductive material in the thickness direction is 5 kV/mm or more.
The heat conductive material according to [1] or [2], wherein a heat conductivity of the heat conductive material in the thickness direction is 2.03 W/mK or more.
The heat conductive material according to any one of [1] to [3], wherein a ratio of the filler with respect to a total of the matrix resin and the filler is 20 mass % or more and less than 50 mass %.
The heat conductive material according to any one of [1] to [4], wherein a ratio of the filler with respect to a total of the matrix resin and the filler is 10 volume % or more and 40 volume % or less.
The heat conductive material according to any one of [1] to [5], wherein a ratio of the filler X with respect to all the filler is 50% or more.
The heat conductive material according to any one of [1] to [6], wherein a ratio of the filler X with respect to all the filler is 70% or more.
The heat conductive material according to any one of [1] to [7], wherein a volume resistivity of the matrix resin is 1012 Ωcm or more.
The heat conductive material according to any one of [1] to [8], wherein a volume resistivity of the second filler is 10−2 Ωcm or less.
The heat conductive material according to any one of [1] to [9], wherein the matrix resin is a cured product of a curable resin.
The heat conductive material according to [10], wherein the curable resin is a thermosetting resin.
The heat conductive material according to [11], wherein the thermosetting resin is a silicone resin or an epoxy resin.
The heat conductive material according to any one of [1] to [12], wherein the first filler is a flake shape, and the second filler is a bar shape.
The heat conductive material according to any one of [1] to [13], wherein a material of the first filer is a boron nitride, an aluminum nitride, a silicon nitride, a beryllia, a magnesia, or an alumina.
The heat conductive material according to any one of [1] to [14], wherein a material of the second filler is a carbon, a metal or a metal oxide.
The heat conductive material according to any one of [1] to [15], wherein the heat conductive material is used in a battery module.
A method for producing the heat conductive material according to any one of [1] to [16], the method comprising:
The method for producing the heat conductive material according to [17], wherein a viscosity of the curable resin is 1 Pa·s or less.
A battery module comprising a battery and a heat radiating material, wherein
The heat conductive material in the present disclosure exhibits an effect of achieving both heat conductivity and insulation properties.
The heat conductive material, the method for producing the heat conductive material, and the battery module in the present disclosure will be hereinafter explained in details with reference to drawings. Each drawing described as below is a schematic view, and the size and the shape of each portion are appropriately exaggerated in order to be understood easily.
As shown in
According to the present disclosure, when the first filler and the second filler of which magnetic susceptibility is different from each other are used, and further when the rate of the filler X is in the specified range, the heat conductive material may achieve both of heat conductivity and insulation properties. As described above, since electronic equipment in recent years has high heat generation density and is often used under high voltage, it is important to secure the heat radiation properties and insulation properties. Also, for example, batteries also generate heat during charge and discharge, and are used under high voltage, and thus it is important to secure the heat radiation properties and insulation properties. A material with high conductivity (low insulation properties) such as a metal is often used as the heat radiating element, and thus the heat conductive material disposed between the heat generating element and the heat radiating element is required to have excellent insulation properties in addition to excellent heat conductivity.
For example, although the boron nitride described in Patent Literature 1 is a material with excellent heat conductivity and insulation properties, it is a flake shape (squamous) powder, and is known to have anisotropic heat conductivity. In specific, the heat conductivity in the thickness direction and the heat conductivity in the in-plane direction (direction orthogonal to the thickness direction) are greatly different, and the latter is especially large. For this reason, in order to express excellent heat conductivity in the thickness direction of the heat conductive material, it is necessary to orient the boron nitride along with the thickness direction of the heat conductive material. For example, Patent Literature 1 discloses an orientation of the boron nitride by applying the magnetic field to the boron nitride, but since the boron nitride has low magnetic field responsiveness (low magnetic susceptibility), it is difficult to orient the boron nitride along with the thickness direction of the heat conductive material, and there is a room for improvement in improving the heat conductivity.
Meanwhile, Patent Literature 2 discloses that the heat conductive particle with high magnetic field responsiveness and the heat conductive particle with low magnetic field responsiveness are used together. Further, Patent Literature 2 discloses that a nickel plated graphite is used as the heat conductive particle with high magnetic field responsiveness, and discloses that the content of the heat conductive particle with high magnetic field responsiveness is more than the content of the heat conductive particle with low magnetic field responsiveness. Since the nickel plated graphite has high electric conductivity, it is difficult to express excellent insulation properties.
Also, Patent Literature 3 discloses a sheet shaped heat radiating material comprising: a heat conductive filler including an agglomerated hexagonal boron nitride powder having a specified orientation property index, and an aluminum oxide powder; and a silicone resin. Since the boron nitride and the aluminum oxide have low magnetic field responsiveness (low magnetic susceptibility), the orientation of the boron nitride along with the thickness direction of the heat conductive material is difficult, and there is a room for improvement in improving the heat conductivity.
In contrast, in the present disclosure, the second filler with high magnetic field responsiveness is used in addition to the first filler with low magnetic field responsiveness, and thus the second filler is a driving force of orienting the first filler. For this reason, orientation of the first filler that is a bar shape or a flake shape along with the thickness direction of the heat conductive material is easy, and further improvement of the heat conductivity may be achieved. Also, the volume resistivity of the first filler is high, and further, since the content of the first filler is more than the content of the second filler, for example, even when the second filler has electric conductivity, excellent insulation properties can be secured. Therefore, both heat conductivity and insulation properties in high level can be achieved.
The filler in the present disclosure includes a first filler that is a bar shape or a flake shape, and a second filler that is a bar shape or a flake shape. In the present disclosure, the “bar shape” includes a shape referred to as a fiber shape or a needle shape, and the “flake shape” includes a shape referred to as a squamous, a thin piece shape or a plate shape.
In the filler, the length of the longest part is regarded as “length a” and the length of the shortest part is regarded as “length b”. As shown in
As shown in
As shown in
The heat conductive material in the present disclosure contains a first filler. The volume resistivity of the first filler is preferably high. In other words, the first filler preferably includes high insulation properties. The reason thereof is to obtain a heat conductive material with excellent insulation properties. The volume resistivity of the first filler is, usually 1012 Ωcm or more, may be 1013 Ωcm or more, and may be 1014 Ωcm or more. The volume resistivity can be obtained by a constant voltage application method.
The magnetic susceptibility of the first filler is preferably low. In other words, the magnetic field responsiveness of the first filler is preferably low. In the present disclosure, the magnetic susceptibility refers to a volume susceptibility (SI unit base). The magnetic susceptibility of the first filler is usually 10−6 or less, and may be 10−7 or less. The first filler has the magnetic susceptibility of 10−6 or less, and may be a paramagnetic material with a positive value, and may be a diamagnetic material with a negative value of the magnetic susceptibility.
The heat conductivity of the first filler is preferably high. By using the first filler with high heat conductivity, a heat conductive material with excellent heat conductivity is obtained. Also, the heat conductivity of the first filler is usually higher than that of the matrix resin. The heat conductivity of the first filler is, for example, 20 W/mK or more, may be 50 W/mK or more, and may be 100 W/mK or more. The heat conductivity of the first filler is, for example, 300 W/mk or less.
The first filler is preferably an inorganic filler. Examples of the material of the first filler may include a boron nitride (BN), an aluminum nitride (AlN), a silicon nitride (Si3N4), a beryllia (BeO), a magnesia (MgO), and an alumina (Al2O3), and among them, the boron nitride (BN) is preferable, and in particular, a hexagonal boron nitride (h-BN) is preferable.
When the aspect ratio designates the above described “a/b, the rate of the length a with respect to the length b”, the aspect ratio in the first filler may be larger than the aspect ratio in the second filler. The reason therefor is to facilitate the orientation of the first filler.
The content of the first filler in the heat conductive material relative to 100 mass parts of the matrix resin is, for example, 25 mass parts or more and 90 mass parts or less, and may be 30 mass parts or more and 80 mass parts or less. Also, in the present disclosure, the content of the first filler is usually more than the content of the second filler. The rate of the first filler with respect to the total of the first filler and the second filler is, for example, 85 mass % or more, may be 90 mass % or more, and may be 95 mass % or more.
The heat conductive material in the present disclosure contains a second filler. The magnetic susceptibility of the second filler is higher than that of the first filler. In other words, the magnetic field responsiveness of the second filler is higher than that of the first filler. The magnetic susceptibility of the second filler is, usually 10−4 or more, and may be 10−3 or more. Meanwhile, the magnetic susceptibility of the second filler is, for example, 106 or less. The second filler may be a paramagnetic material of which magnetic susceptibility is 10−4 or more and 10−3 or less, may be a ferromagnetic material of which magnetic susceptibility is 102 or more, and may be a diamagnetic material of which magnetic susceptibility is a negative value.
There are no particular limitations on the volume resistivity of the second filler. The second filler may be a conductor of which volume resistivity is 10−2 Ωcm or less, may be a semiconductor of which volume resistivity is larger than 10−2 Ωcm and less than 104 Ωcm, and may be an insulating material of which volume resistivity is 104 Ωcm or more. The volume resistivity can be obtained by a constant current application method or a constant voltage application method.
The heat conductivity of the second filler is preferably high. By using the second filler with high heat conductivity, a heat conductive material with high heat conductivity is obtained. Also, the heat conductivity of the second filler is usually higher than that of the matrix resin. The heat conductivity of the second filler is preferably higher than that of the first filler.
The second filler is preferably an inorganic filler. Examples of the material of the second filler may include a carbon, a metal and a metal oxide. Examples of the metal may include a nickel, an iron and a cobalt. Examples of the metal oxide may include an iron oxide, a chrome oxide, and a ferrite. Specific examples of the second filler may include a carbon fiber, a metal fiber and a metal oxide fiber. For example, when the second filler is a bar shape, the second filler may include a base material that is the bar shape, and a coating layer that covers a surface of the base material. Examples of the bar shape based material may include a carbon fiber, a metal fiber and a resin fiber. The coating layer preferably contains the above described carbon, metal or metal oxide. Specific examples of such a second filler may include a filler including a carbon fiber and a nickel layer that covers a surface of the carbon fiber.
The content of the second filler in the heat conductive material relative to 100 mass parts of the matrix resin is, for example, 0.2 mass parts or more and 15 mass parts or less, and may be 1 mass part or more and 10 mass parts or less.
The heat conductive material in the present disclosure usually contains the first filler and the second filler as a main component of the filler. The heat conductive material may contain just the first filler and the second filler, and may further include an additional filler in addition to the first filler and the second filler. The ratio of the total of the first filler and the second filler with respect to all the fillers included in the heat conductive material is, usually 50 mass % or more, may be 70 mass % or more, and may be 90 mass % or more.
The ratio of the filler with respect to the total of the matrix resin and the filler is, for example, 20 mass % or more and less than 50 mass, and may be 25 mass % or more and 45 mass % or less. Also, the ratio of the filler with respect to the total of the matrix resin and the filler is, for example, 10 volume % or more and 40 volume % or less, and may be 15 volume % or more and 35 volume % or less.
As shown in
The heat conductive material in the present disclosure contains a matrix resin. The matrix resin preferably has high volume resistivity. In other words, the matrix resin preferably has high insulation properties. The volume resistivity of the matrix resin is, for example, 1012 Ωcm or more, may be 1013 Ωcm or more, and may be 1014 Ωcm or more. The volume resistivity can be obtained by a constant voltage application method.
The magnetic susceptibility of the matrix resin is usually low. The magnetic susceptibility of the matrix resin is, for example, 10−6 or less and may be 10−7 or less. Also, the heat conductivity of the matrix resin is usually lower than that of the filler. The heat conductivity of the matrix resin is, for example, 1 W/mK or less, may be 0.5 W/mK or less.
The matrix resin is preferably a cured product of a curable resin. The curable resin may be a thermosetting resin, and may be an ionizing radiation curable resin. Examples of the thermosetting resin may include a silicone resin and an epoxy resin. Examples of the silicone resin may include a straight silicone resin such as a methyl silicone resin, a methyl phenyl silicone resin, and a phenyl silicone resin; and an organic resin modified silicone resin such as an alkyd modified silicone resin, a polyester modified silicone resin, an urethane modified silicone resin, an epoxy modified silicone resin, and an acryl modified silicone resin. Also, examples of a curing agent that cures the silicone resin may include a normal temperature curing agent such as an organic titanate-based curing agent; a catalyst type curing agent such as a zinc dioctoate; and a reactive type curing agent such as a silane coupling agent.
Examples of the epoxy resin may include a bis phenol A type epoxy resin, a novolac type epoxy resin, an alicyclic type epoxy resin, a long-chain aliphatic type epoxy resin, a glycidyl ester type epoxy resin, and a glycidyl amine type epoxy resin. Also, examples of the curing agent that cures the epoxy resin may include an amine-based curing agent, an acid anhydrite-based curing agent, and a polyamide curing agent. Also, the thermosetting resin may be a one liquid curing type, and may be a two liquid curing type.
The content of the matrix resin in the heat conductive material is, for example, 50 mass % or more and 85 mass % or less, and may be 60 mass % or more and 80 mass % or less.
The heat conductive material in the present disclosure contains a matrix resin and a filler. The details of the matrix resin and the filler are as described above. The dielectric breakdown voltage of the heat conductive material in the thickness direction is preferably high. In specific, the dielectric breakdown voltage of the heat conductive material in the thickness direction is preferably 5 kV/mm or more. Also, the heat conductivity of the heat conductive material in the thickness direction is preferably high. In specific, the heat conductivity of the heat conductive material in the thickness direction is, for example, 2.03 W/mK or more, may be 2.36 W/mK or more, and may be 3.14 W/mK or more.
There are no particular limitations on the shape of the heat conductive material, and examples thereof may include a sheet shape. The “sheet shape” includes a shape referred to as a film shape or a plate shape. Also, the heat conductive material may be an arbitrary three-dimensional shape. Also, there are no particular limitations on the applications of the heat conductive material, and examples thereof may include a battery module; electronic parts such as LED and home appliances; and an information communication module such as optical communication apparatus.
According to the present disclosure, when the first filler and the second filler of which magnetic susceptibility differs from one another are used, and the curable resin is cured while applying a magnetic field, the heat conductive material that achieves both heat conductivity and insulation properties is obtained.
The precursor layer forming step in the present disclosure is a step of forming a precursor layer using a resin composition containing a curable resin for forming the matrix resin, and the filler.
The resin composition includes the first filler and the second filler as the filler. Also, the resin composition may contain a curing agent that cures the curable resin. The details of the curable resin, the filler and the curing agent are in the same contents as those described in “A. Heat conductive material” above. The viscosity of the curable resin is, for example, preferably 1 Pa·s or less. The reason therefor is to facilitate orientation of the filler along with the magnetic field to be applied when curing the curable resin. Examples of the method for forming the precursor layer may include a method of coating the base material with the resin composition. There are no particular limitations on the kind of the base material, and examples thereof may include a heat radiating material.
The curing step in the present disclosure is a step of curing the curable resin by applying a magnetic field to the precursor layer from the thickness direction while orienting the filler in the precursor layer.
The magnetic field is applied to the precursor layer from the thickness direction. Thereby, bar shape or flake shape filler is oriented along with the thickness direction. The magnetic flux density of the magnetic field to be applied is not particularly limited, and for example, it is 0.5 T or more and 10 T or less. When the curable resin is a thermosetting resin, the thermosetting resin may be cured at a normal temperature (room temperature), and the thermosetting resin may be cured by heating. Meanwhile, when the curable resin is an ionizing radiation curable resin, the ionizing radiation curable resin is cured by irradiating an ionizing radiation ray (such as an ultraviolet ray).
The heat conductive material obtained by the above described steps is in the same contents as those described in “A. Heat conductive material” above; thus, the descriptions herein are omitted.
According to the present disclosure, when the above described heat conductive material is disposed between the battery and the heat radiating material, the battery module may have excellent heat radiation properties and insulation properties.
The battery in the present disclosure usually includes at least one cell. The cell usually includes a power generating element and an outer package that covers the power generating element. The power generating element usually includes at least one power generating unit including a cathode, an anode, and an electrolyte layer disposed between the cathode and the anode. The battery 20 shown in
The heat radiating material in the present disclosure is a material that receives heat generated by a chemical reaction of a battery, and radiates heat to the other medium. There are no particular limitations on the kind of the heat radiating material, and known heat radiating materials (such as a cooling material) can be used.
The heat conductive material in the present disclosure is disposed between the battery and the heat radiating material. The heat conductive material is in the same contents as those described in “A. Heat conductive material” above.
Examples of the applications of the battery module in the present disclosure may include a power source for vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery electric vehicles (BEV), gasoline-fueled automobiles and diesel powered automobiles. In particular, it is preferably used as a power source for driving hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV). Also, the battery module in the present disclosure may be used as a power source for moving bodies other than vehicles (such as rail road transportation, vessel and airplane), and may be used as a power source for electronic products such as information processing equipment.
The present disclosure is not limited to the embodiments. The embodiments are exemplification, and any other variations are intended to be included in the technical scope of the present disclosure if they have substantially the same constitution as the technical idea described in the claims of the present disclosure and have similar operation and effect thereto.
As a thermosetting resin, a normal temperature curable silicone resin (viscosity: 650 mPa·s, volume resistivity: 1014 Ωcm to 1016 Ωcm, from Shin-Etsu Chemical Co., Ltd.) was prepared, as a first filler, a boron nitride (from Momentive) was prepared, and as a second filler, a carbon fiber (from Mitsubishi Chemical Group Corporation) was prepared. The details of the first filler and the second filler are as follows.
The thermosetting resin was weighed to be 75 mass parts, the first filler was weighed to be 24 mass parts, and the second filler was weighed to be 1 mass part, and those were mixed and agitated using a rotating/revolving mixer. The obtained composition was poured into a container for curing (10 mm thick), and placed still for 90 minutes at a normal temperature while applying magnetic field with magnetic flux density of 8T from up and down surfaces of the thickness direction using a magnetic field forming device with a pulse magnetizing coil, and thereby the thermosetting resin was cured. In this manner, a sheet shape heat conductive material was obtained.
A heat conductive material was respectively obtained in the same manner as in Example 1, except that the blending amount of the thermosetting resin, the first filler and the second filler was respectively changed as shown in Table 3.
A heat conductive material was respectively obtained in the same manner as in Example 1, except that the blending amount of the thermosetting resin, the first filler and the second filler was respectively changed as shown in Table 4, and further, the magnetic field was not applied.
The rates of the filler X in the heat conductive materials obtained in Examples 1 to 4 and Comparative Examples 1 to 11 were measured. In specific, cross-sectional images were prepared by a CT detecting device, the cross-sectional images were binarized, and the angles of the fillers in the binarized images were measured to produce histograms. The results are shown in Table 3 and Table 4. Also,
The heat conductivity of the heat conductive materials obtained in Examples 1 to 4 and Comparative Examples 1 to 11 was respectively measured. In specific, the heat conductivity of the heat conductive materials was measured by a steady state method (heat flowmeter method). The results are shown in Table 3 and Table 4.
The dielectric breakdown voltage (BDV) of the heat conductive materials obtained in Examples 1 to 4 and Comparative Examples 1 to 11 was respectively measured. In specific, in accordance with IEC 60243-1, the voltage when dielectric breakdown occurred was divided by the thickness of the heat conductive material to obtain the dielectric breakdown voltage. The results are shown in Table 3 and Table 4.
In Comparative Examples 7 to 10, both of the first filler and the second filler were used, but the magnetic field was not applied when curing the thermosetting resin, and thus the filler was not oriented along with the thickness direction, and the heat conductivity in the thickness direction was low. Also, in Comparative Examples 7 to 10, the heat conductivity did not improve even when the filler amount was increased. In Comparative Example 10, degrade in the dielectric breakdown voltage was confirmed. This is presumably because the ratio of the second filler that had high conductivity was too much. Also, in Comparative Example 11, the second filler was used, but the first filler that had high heat conductivity was not used, and further, the magnetic field was not applied when curing the thermosetting resin, and thus the heat conductivity was low. Also, since the second filler had high conductivity, the dielectric breakdown voltage was low, and thus excellent insulation properties were not obtained.
In Comparative Examples 1 to 3, the first filler was used, and the second filler was not used, but the magnetic field was applied when curing the thermosetting resin, and thus the filler was oriented along with the thickness direction, and the heat conductivity was comparatively high. Also, in Comparative Examples 1 to 3, when the filler amount was increased, the heat conductivity improved, and the dielectric breakdown voltage was also high.
In Examples 1 and 4, since both of the first filler and the second filler were used, and the magnetic field was applied when curing the thermosetting resin, the filler was oriented along with the thickness direction, and the heat conductivity was remarkably high. When comparing Examples 1 to 3 to Comparative Examples 1 to 3, the heat conductivity in Examples 1 and 3 was higher than the heat conductivity in Comparative Examples 1 to 3. This is presumably because the orientation of the first filler was improved by using the second filler of which magnetic field responsiveness was high. In other words, it was confirmed that a synergistic effect was obtained when both of the first filler and the second filler were used. Also, in Examples 1 and 4, when the filler amount was increased, the heat conductivity improved, and the dielectric breakdown voltage was also high. In this manner, it was confirmed that the heat conductive material that achieves both the heat conductivity and the insulation properties was obtained when the first filler and the second filler of which magnetic susceptibility differs from one another were used, and further when the rate of the filler X was in the specified range.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-083094 | May 2023 | JP | national |
