JP2017065984A - Ceramic particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device which can be used without power supply, can be miniaturized, and has excellent moisture resistance and insulating properties.SOLUTION: A ceramic particle includes a core part of a ceramic material containing vanadium oxide and a coating of a material having a rutile structure covering the surface thereof.SELECTED DRAWING: None

Description

  The present invention relates to ceramic particles, in particular particles of a ceramic material containing vanadium oxide.

  The number of electronic components such as CPU (central processing unit), power amplifier, FET (field effect transistor), IC (integrated circuit), voltage regulator, etc., which become heat sources, has increased due to the recent improvement in performance of electronic devices. The increase in energy generated overlaps with the problem of heat generation. In particular, mobile devices such as smartphones and tablet terminals have a problem that the heat deteriorates the capacity of the battery and seriously affects the reliability of the electronic devices to be configured. Therefore, it is required to control the temperature inside the device to a higher degree.

  Control of the heat generated from the heat source as described above is performed by a cooling fan, a heat pipe, a heat sink, a thermal sheet, a Peltier element, or the like, which is an existing heat management solution. A cooling device in which a fan or a Peltier element is combined is described (see Patent Document 1).

  However, the cooling device combining the heat sink and the fan or the Peltier element as described above has a relatively complicated structure and increases the size of the device, particularly for thin devices such as smartphones and tablet terminals. Hateful. Furthermore, since power is consumed, it is disadvantageous from the viewpoint of low power consumption (battery life).

  Therefore, in thin devices such as smartphones and tablet terminals, the temperature is currently controlled only by means of heat dissipation through the housing, and the heat source and the housing are thermally coupled by a thermal sheet or the like to release heat.

JP 2010-223497 A

  There is a limit to the heat radiation through the casing as described above because the surface area of the casing is limited. Therefore, the temperature of each heat source is measured, and when the temperature exceeds a predetermined temperature, the performance of the CPU or the like is limited (suppressing heat generation itself). That is, the temperature rise of the housing may hinder the performance of the CPU or the like. Naturally, in heat dissipation through such a case, in other words, heat dissipation by heat transfer to the entire device, heat is also transferred to the battery, which can lead to a decrease in battery capacity over time.

In view of this, the present inventor has arranged vanadium oxide (specifically, vanadium dioxide), which is a ceramic material that absorbs heat accompanying a crystal structure phase transition or a magnetic phase transition, by placing it near the heat source of an electronic device. We considered a cooling device that can be used with a power supply. However, studies by the present inventor have revealed that general vanadium dioxide (VO ₂ ) exhibits a good endothermic effect in the initial stage, but the endothermic effect gradually decreases in a high humidity environment. Therefore, when vanadium dioxide is used as a cooling device, a strong packaging is necessary to avoid contact with moisture (water vapor), which increases the cost and greatly restricts the shape of the device. The problem arises.

  Furthermore, vanadium dioxide is conductive and requires an insulation treatment when used in electronic equipment. In order to ensure insulation, it is necessary to form an insulating layer on the contact surface with the electronic device or package it with an insulating material such as a resin. Also in this case, there is a problem that the cost is increased and it is difficult to reduce the size by the insulating layer.

  Accordingly, an object of the present invention is to provide ceramic particles containing vanadium oxide that are excellent in moisture resistance, prevent deterioration of endothermic characteristics due to moisture, and further ensure insulation.

  As a result of intensive studies to solve the above problems, the present inventors have formed a layer of a material having a rutile structure on the surface of vanadium oxide that absorbs heat in accordance with a crystal structure phase transition or a magnetic phase transition. It has been found that ceramic particles that can solve the above-described problems can be obtained by the formation, and the present invention has been achieved.

  According to the first aspect of the present invention, there is provided a ceramic particle having a core portion of a ceramic material containing vanadium oxide and a coating of a material having a rutile structure covering the surface thereof.

  According to a second aspect of the present invention, there is provided a composition for manufacturing a cooling device comprising the ceramic particles.

  According to a third aspect of the present invention, there is provided a cooling device comprising the ceramic particles.

  According to a fourth aspect of the present invention, there is provided an electronic component comprising the above cooling device.

  According to a fifth aspect of the present invention, there is provided an electronic apparatus comprising the cooling device or the electronic component.

  According to the present invention, by applying a coating of a material having a rutile structure on the surface of a core portion of a ceramic material that absorbs heat accompanying a crystal structure phase transition or a magnetic phase transition, moisture resistance and insulation of the ceramic material are achieved. Can be greatly improved.

  The ceramic material used in the present invention is a ceramic material that absorbs heat by latent heat, and is specifically a ceramic material containing vanadium oxide (typically vanadium dioxide).

  The absorption of heat by this ceramic material is done by absorbing latent heat. Such a ceramic material can obtain a high cooling effect by temporally smoothing the heat by temporarily absorbing excess heat by latent heat.

  The ceramic material is preferably composed mainly of vanadium oxide, typically vanadium dioxide.

  The “main component” means a component contained in the ceramic material by 60% by mass or more, particularly 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 98% by mass. For example, it means a component contained in, for example, 98.0 to 99.8 mass% or substantially 100%.

Impurities in the ceramic material are not particularly limited, but vanadium oxides other than the vanadium oxide described below, such as V ₂ O ₃ and V ₂ O ₅ , other ceramic materials such as glass, and Na, Al, Cr, Fe Ni, Mo, Sb, Ca, Si, and oxides thereof.

  In one embodiment, the vanadium oxide contains vanadium and M (wherein M is at least one selected from W, Ta, Mo and Nb), and the total amount of vanadium and M is 100 mol parts. V may be vanadium oxide in which the molar part of M is 0 mol part or more and about 5 mol part or less. Note that M is not an essential component, and the content molar part of M may be 0.

In another embodiment, the vanadium oxide has the formula:
V _1-x M _x O ₂
(In the formula, M is W, Ta, Mo or Nb, and x is 0 or more and 0.05 or less.)
Or one or more vanadium oxides represented by

In a preferred embodiment, the vanadium oxide has the formula:
V _1-x W _x O ₂
(In the formula, x is 0 or more and 0.01 or less.)
Or one or more vanadium oxides represented by

  In one embodiment, the vanadium oxide is a composite oxide containing A (where A is Li or Na) and vanadium, and the content of A when the vanadium is 100 mol parts is about The composite oxide may be 50 to about 110 parts by mole, preferably about 70 to about 110 parts by mole, more preferably about 70 to about 98 parts by mole.

Further, the vanadium oxide is a composite oxide containing A (where A is Li or Na), vanadium and a transition metal (for example, at least one selected from titanium, cobalt, iron and nickel). And
The molar ratio of vanadium to transition metal is in the range of 995: 5 to 850: 150;
The composite oxide may be characterized in that the total ratio of vanadium and transition metals and the molar ratio of A is in the range of 100: 70 to 100: 110.

In another embodiment, the vanadium oxide has the formula:
^{_{A y V 1-z M a}} z O 2
(Wherein A is Li or Na, M ^a is a transition metal; y is 0.5 or more and 1.1 or less, preferably y is 0.7 or more and 1.1 or less. And z is 0 or more and 0.15 or less.)
Or one or more vanadium oxides represented by

In the above formula, preferably, A is Li. Also preferably, M ^a is at least one metal selected titanium, cobalt, iron and nickel.

In a preferred embodiment, in the above formula, y and z satisfy either of the following (a) or (b).
(A) 0.70 ≦ y ≦ 0.98 and z = 0, or (b) 0.70 ≦ y ≦ 1.1 and 0.005 ≦ z ≦ 0.15

In one embodiment, the vanadium oxide is Ti-doped vanadium oxide or vanadium oxide further doped with other atoms selected from the group consisting of W, Ta, Mo and Nb,
When the other atom is W, the content mole part of the other atom is greater than 0 mole part and less than or equal to 5 mole part with respect to a total of 100 mole parts of vanadium, Ti, and other atoms,
When the other atom is Ta, Mo or Nb, the content mole part of the other atom is greater than 0 mole part and 15 mole parts or less with respect to 100 mole parts in total of vanadium, Ti and other atoms,
The content mole part of titanium is not less than 2 mole parts and not more than 30 mole parts with respect to 100 mole parts in total of vanadium, Ti and other atoms. By using such vanadium oxide, the moisture resistance of the ceramic material is further improved.

  In a preferred embodiment, the Ti-doped vanadium oxide may contain 5 to 10 mol parts of titanium with respect to 100 mol parts of Ti and other atoms in total.

  In the present invention, “Ti-doped vanadium dioxide” means vanadium oxide showing a corresponding crystal structure by X-ray structural analysis (typically using a powder X-ray diffraction method). In this specification, “vanadium dioxide doped with other atoms” means vanadium dioxide doped with other atoms in addition to Ti, and means vanadium oxide showing a corresponding crystal structure by X-ray structural analysis. To do.

In another embodiment, the vanadium oxide is
_{Formula: V 1-x-y Ti} x M y O 2
[Wherein M is W, Ta, Mo or Nb;
x is 0.02 or more and 0.30 or less,
y is 0 or more,
When M is W, y is 0.05 or less,
When M is Ta, Mo or Nb, y is 0.15 or less. ]
It is vanadium oxide represented by these. By using such vanadium oxide, the moisture resistance of the ceramic material is improved.

  Preferably, in the above formula, x may be 0.05 or more and 0.10 or less.

  The temperature at which the vanadium oxide undergoes phase transition is appropriately selected according to the object to be cooled, the purpose of cooling, and the like. For example, when the object to be cooled is a CPU, the temperature is 20 to 100 ° C., preferably 40 to 60 ° C. It is preferable to transfer. The temperature at which the vanadium oxide undergoes phase transition, that is, the temperature at which the vanadium oxide exhibits latent heat, can be adjusted by adding (doping) other atoms and adjusting the amount of the atoms added.

  The vanadium oxide has an initial latent heat amount of preferably 35 J / g or more, more preferably 45 J / g or more, and still more preferably 50 J / g or more. By having a larger amount of latent heat, a large cooling effect can be exhibited with a smaller volume, which is advantageous in terms of downsizing. Here, “latent heat” is the total amount of thermal energy required when the phase of a substance changes, and in this specification, it is a solid-solid phase transition, for example, an electric, magnetic, or structural phase transition. This refers to the amount of heat generated and absorbed.

  The core part made of a ceramic material is in the form of particles (powder). The average particle size (D50: the particle size at which the cumulative value is 50% in a cumulative curve with a particle size distribution determined on a volume basis and the total volume being 100%) of the core portion composed of the ceramic material is particularly Although not limited, for example, 0.1 μm to several hundred μm, specifically 0.1 μm to 900 μm, typically 1.0 μm to 100 μm, for example, 10 μm to 80 μm or 30 μm to 50 μm. possible. The average particle diameter can be measured using a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus or an electronic scanning microscope. The average particle diameter is preferably 0.1 μm or more from the viewpoint of ease of handling and ease of coating, and is preferably 50 μm or less from the viewpoint of being able to be molded more densely.

  The material having a rutile structure that covers the core portion composed of a ceramic material is not particularly limited as long as it has a rutile structure, and examples thereof include titanium (IV) oxide and manganese (IV) oxide, preferably Titanium oxide (IV).

The titanium oxide (IV) and manganese oxide (IV) are represented by TiO _x and MnO _x , respectively, and x may preferably be 2, but may be slightly deviated from 2 due to oxygen defects or the like.

  The thickness of the coating of the material having a rutile structure that covers the core portion made of the ceramic material is not particularly limited, but is preferably 5 nm to 5 μm, more preferably 10 nm to 1.0 μm, for example, 50 nm to 500 nm. It can be. By setting the thickness to 5 nm or more, moisture resistance and insulation can be ensured more reliably. On the other hand, when the thickness is 10 μm or less, the ceramic particles can be made smaller, and the ceramic particles can be provided even in a finer region. In addition, the influence of stress due to the difference in coefficient of thermal expansion with the ceramic particles can be reduced.

  The method for coating the core with a material having a rutile structure is not particularly limited, but it is preferable to coat by a vapor phase method, and typically the coating is performed by sputtering or chemical vapor deposition (CVD).

  The material having a rutile structure preferably covers the entire core portion substantially composed of a ceramic material.

  The average particle diameter (D50) of the ceramic particles of the present invention is not particularly limited, but is, for example, 0.1 μm to several hundred μm, specifically 0.1 μm to 900 μm, typically 0.2 μm to 50 μm. For example, it may be 0.5 μm or more and 50 μm or less, or 1.0 μm or more and 30 μm or less. The average particle diameter can be measured using a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus or an electronic scanning microscope. The average particle diameter is preferably 0.1 μm or more from the viewpoint of ease of handling and moisture resistance, and is preferably 50 μm or less from the viewpoint of being able to be molded more densely.

  The ceramic particles of the present invention have high endothermic properties and have high moisture resistance because the surface is coated with a material having a rutile structure. At the same time, by making the material having a rutile structure an insulating material such as titanium (IV) oxide or manganese (IV) oxide, high insulating properties can be obtained. Such ceramic particles can be suitably used as a cooling device.

  Accordingly, the present invention also provides a cooling device including the ceramic particles. The ceramic particles of the present invention can themselves be used as a particulate cooling device, but are preferably used after being molded.

  When molded and used, the content of the ceramic particles in the cooling device is preferably 20 vol% or more, more preferably 30 vol% or more, more preferably 50 vol% or more, with respect to the entire cooling device, from the viewpoint of obtaining a larger endothermic amount. For example, 60% or more or 70% or more is more preferable. Moreover, from the viewpoint of ensuring the strength of the cooling device, it is preferably 90 vol% or less, more preferably 80 vol% or less, with respect to the entire cooling device.

  Although it does not specifically limit as another component contained in a molded object, Various additives, for example, resin, binder, glass, etc. are mentioned. These additives can be appropriately selected according to, for example, characteristics, shapes, manufacturing methods, and the like required for the cooling device.

  The shape of the cooling device of the present invention is not particularly limited, and can be any shape.

  In one embodiment, the cooling device of the present invention may be block-shaped. By making it into a block shape, the whole volume becomes large and more heat can be absorbed. In another aspect, the cooling device of the present invention may be in the form of a sheet. By making it into a sheet shape, the surface area increases, so it becomes easy to release absorbed heat to the outside.

  The cooling device having such a shape can be manufactured by a method generally used in the art, for example, by compressing ceramic particles. Moreover, the paste containing ceramic particles can be laminated and compression molded. Furthermore, it can also be obtained by separately forming a ceramic sheet and pressing it.

  In another aspect, in the cooling device of the present invention, ceramic particles are dispersed in an insulating resin to give fluidity, thereby forming a composition for manufacturing a cooling device (for example, a paste), which is a predetermined component of an electronic device. It may be obtained by providing to a spot where it is cured and / or solidified. Accordingly, the present invention also provides a composition for manufacturing a cooling device comprising the ceramic particles of the present invention.

  Since the composition for manufacturing a cooling device has fluidity, it has a shape corresponding to a location to be provided, and is substantially cured and / or solidified in that shape to form a cooling device. Therefore, it can become a cooling device of arbitrary shapes, and can be installed also in the location which has a fine and complicated shape. In addition, since the ceramic particles contained in the composition for manufacturing a cooling device of the present invention can be insulative, the cooling device can also be provided directly on the electronic component, that is, the cooling device is installed directly on the electronic component. can do.

  It does not specifically limit as insulating resin contained in the composition for cooling device manufacture, For example, various thermosetting resins and thermoplastic resins can be used.

  Although it does not specifically limit as said thermosetting resin, For example, a urethane resin, an epoxy resin, a polyimide resin, a silicone resin, a fluorine resin, a liquid crystal polymer resin, and a polyphenyl sulfide resin are mentioned. These may be used alone or in admixture of two or more.

  When a thermosetting resin is used as the insulating resin, the cooling device manufacturing composition may contain a curing agent as desired. Such a curing agent is not particularly limited, and examples thereof include phenol resins, polyamines, and imidazoles.

  Although it does not specifically limit as said thermoplastic resin, For example, polyethylene, a polypropylene, a polyvinyl chloride, a polystyrene, a polyvinyl acetate, an acrylic resin, nylon, and polyester are mentioned. These may be used alone or in admixture of two or more.

  The insulating resin to be used can be appropriately selected according to the type and application of the electronic device in which the cooling device is installed. For example, when used for general electronic equipment, an epoxy resin or polyimide resin having solder heat resistance and high versatility is preferable. When used for equipment requiring heat resistance, a glass such as a phenol novolac type epoxy resin or polyimide resin is used. A resin having a transition temperature of 150 ° C. or higher is preferred. In order to increase the thermal conductivity of the cooling device, it is preferable to use a liquid crystal polymer resin having a mesogenic group.

  Further, since the insulating resin can have elasticity, stress applied to the electronic device due to a temperature change can be relieved.

  The composition for manufacturing a cooling device may further contain a solvent.

  The solvent can be appropriately selected from general-purpose solvents according to various factors such as the type and amount of the insulating resin to be used and the characteristics required for the cooling device manufacturing composition. For example, dipropylene methyl ether acetate , Toluene, methyl ethyl ketone and the like are used.

  The composition for manufacturing a cooling device may further contain additives such as a dispersant, a curing accelerator, and an antifoaming agent. A dispersing agent, a hardening accelerator, an antifoaming agent, etc. can be suitably selected as needed from what is used in a general polymer composition.

  The composition for producing a cooling device is not particularly limited, and can be produced, for example, by mixing the ceramic material, the insulating resin, and optionally a curing agent, a solvent, and an additive with a commercially available mixer or the like.

  The present invention also provides an electronic component and an electronic apparatus having the cooling device of the present invention.

  The electronic component is not particularly limited, but for example, an integrated circuit (IC) such as a central processing unit (CPU), a power management IC (PMIC), a power amplifier (PA), a transceiver IC, and a voltage regulator (VR). Light emitting diodes (LEDs), incandescent bulbs, semiconductor lasers and other light emitting elements, field effect transistors (FETs) and other components that can be heat sources, and other components such as substrates, heat sinks, housings, etc. Examples of parts that are commonly used.

  Although it does not specifically limit as an electronic device, For example, a mobile telephone, a smart phone, a personal computer (PC), a tablet-type terminal etc. are mentioned.

Synthesis example 1
Production of vanadium dioxide As ceramic raw materials, vanadium trioxide (V ₂ O ₃ ) and vanadium pentoxide (V ₂ O ₅ ) were used and weighed so that V: O = 1: 2 (molar ratio). Dry mixed. Then, heat treatment was performed at 1000 ° C. for 4 hours in a nitrogen / hydrogen / water atmosphere to prepare VO ₂ powder as a ceramic material. As a result of measuring the particle size of the obtained powder using a microtrack measuring apparatus (laser diffraction / scattering method), D50 was 40 μm.

Example 1
Coating The powder of the ceramic material produced in Synthesis Example 1 was coated with TiO ₂ using sputtering to obtain the ceramic particles of the present invention. As a result of measuring the thickness of TiO ₂ using a TEM (transmission electron microscope), it was 20 nm.

Comparative Example Ceramic particles of a comparative example were obtained in the same manner as in Example 1 except that instead of TiO ₂ , the coating was performed with SiO ₂ .

Test Example 1: Moisture resistance test The initial latent heat of the VO ₂ powder produced in Synthesis Example 1 and the ceramic particles produced in Example 1 and Comparative Example 1 were measured in a nitrogen atmosphere by the DSC (Differential Scanning Calorimetry) method. Temperature rising rate: 10 K / min, sweeping from 0 ° C. to 100 ° C. and then 0 ° C., and the endothermic amount at the time of temperature rising was defined as latent heat amount

  The sample was subjected to a moisture resistance test by leaving it in an environment of 85 ° C. and a relative humidity of 85%. The amount of latent heat was measured again after 100 hours and 300 hours. Table 1 shows the results of measuring the amount of latent heat. The amount of change in latent heat from the beginning is shown in parentheses.

From the above results, it was confirmed that the ceramic particles of the present invention coated with TiO ₂ have high moisture resistance.

Test Example 2: Insulation Test Using a powder resistance system, the resistance values of the VO ₂ powder produced in Synthesis Example 1 and the ceramic particles produced in Example 1 and Comparative Example 1 were measured. Specifically, ceramic particles are filled in a die of a cylindrical press die whose inner surface is insulation-coated, and the resistance value between both ends of the opening is measured while pressing from one end of the opening, and the resistivity Asked.

From the above results, it was confirmed that the ceramic particles of the present invention coated with TiO ₂ have high insulating properties.

  The cooling device of the present invention can be used, for example, as a cooling device for a small communication terminal in which the heat countermeasure problem has become remarkable.

Claims (17)

  A ceramic particle having a core portion of a ceramic material containing vanadium oxide and a coating of a material having a rutile structure covering the surface thereof.   The ceramic particle according to claim 1, wherein the material having a rutile structure is titanium (IV) oxide.   3. The ceramic particle according to claim 1, wherein the thickness of the film of the material having a rutile structure is 5 nm or more and 5 μm or less.   The ceramic particle according to any one of claims 1 to 3, wherein an average particle size is 0.2 µm or more and 50 µm or less.   The ceramic particle according to any one of claims 1 to 4, wherein a film of a material having a rutile structure is formed by a vapor phase method.   Vanadium oxide is an oxide containing V and M (where M is at least one selected from W, Ta, Mo and Nb), and the total of V and M is 100 mol parts The ceramic particle according to any one of claims 1 to 4, wherein a molar part of M is about 0 to about 5 parts by mole. Vanadium oxide has the formula:
V _1-x M _x O ₂
(In the formula, M is W, Ta, Mo or Nb, and x is 0 or more and 0.05 or less)
The ceramic particle according to claim 1, wherein the ceramic particle is an oxide represented by the formula:   Vanadium oxide is an oxide containing A (here, A is Li or Na) and V, and the content of A when V is 100 mol parts is about 50 mol parts or more and about 100 mols The ceramic particles according to any one of claims 1 to 4, wherein the ceramic particles are at most parts. Vanadium oxide has the formula:
A _y VO ₂
(In the formula, A is Li or Na, and y is 0.5 or more and 1.0 or less)
The ceramic particle according to claim 1, wherein the ceramic particle is an oxide represented by the formula: The vanadium oxide is Ti-doped vanadium oxide or further vanadium oxide doped with other atoms selected from the group consisting of W, Ta, Mo and Nb,
When the other atom is W, the content mole part of the other atom is greater than 0 mole part and less than or equal to 5 mole part with respect to a total of 100 mole parts of vanadium, Ti, and other atoms,
When the other atom is Ta, Mo or Nb, the content mole part of the other atom is greater than 0 mole part and 15 mole parts or less with respect to 100 mole parts in total of vanadium, Ti and other atoms,
The content mol part of titanium is 2 mol part or more and 30 mol part or less with respect to a total of 100 mol parts of vanadium, Ti, and other atoms, In any one of Claims 1-4 characterized by the above-mentioned. The ceramic particles described.   11. The ceramic particle according to claim 10, wherein a content mole part of titanium is not less than 5 mole parts and not more than 10 mole parts with respect to 100 mole parts in total of vanadium, Ti, and other atoms. Vanadium oxide has the formula:
_{V 1-x-y Ti x} M y O 2
[Wherein M is W, Ta, Mo or Nb;
x is 0.02 or more and 0.3 or less,
y is 0 or more,
When M is W, y is 0.05 or less,
When M is Ta, Mo or Nb, y is 0.15 or less. ]
The ceramic particles according to claim 1, wherein the ceramic particles are vanadium oxide represented by the formula:   The ceramic particles according to claim 12, wherein x is 0.05 or more and 0.1 or less.   The composition for cooling device manufacture containing the ceramic particle of any one of Claims 1-13.   A cooling device comprising the ceramic particles according to claim 1.   An electronic component comprising the cooling device according to claim 15.   An electronic apparatus comprising the cooling device according to claim 15 or the electronic component according to claim 16.