JPWO2005033216A1 - Highly filled coated magnesium oxide powder and resin composition containing the powder - Google Patents

Abstract

When used as a filler in a resin with excellent moisture resistance, the coated magnesium oxide powder is excellent in fillability and fluidity, the surface is coated with a double oxide, the angle of repose is 55 degrees or less, and the tap density is 1 A coated magnesium oxide powder characterized in that it is greater than or equal to .65 g / ml is provided. Moreover, the resin composition containing this powder and the electronic device using the resin composition are provided.

Description

  The present invention relates to a coated magnesium oxide powder excellent in moisture resistance and excellent in filling properties when used as a filler, and a resin composition excellent in fluidity containing the coated magnesium oxide powder.

The electronic device is composed of electronic components such as a laminate, a printed wiring board, and a multilayer wiring board. In electronic parts, resin compositions are usually used for prepregs, spacers, sealants, adhesive sheets, and the like, and various performances or characteristics are required for resin compositions. For example, as a recent trend, high-capacity power element mounting and high-density mounting are seen in electronic devices, and accordingly, heat dissipation and moisture resistance superior to conventional ones are required for resin compositions and applied products. Yes.
Conventionally, silicon dioxide (hereinafter referred to as silica) and aluminum oxide (hereinafter referred to as alumina) have been used as fillers used in resin compositions for semiconductor encapsulation. However, the thermal conductivity of silica is low, and heat dissipation corresponding to an increase in the amount of heat generated due to high integration, high power, high speed, etc. is insufficient, causing problems in stable operation of the semiconductor. On the other hand, when alumina having higher thermal conductivity than silica is used, the heat dissipation is improved, but since alumina has a high hardness, there has been a problem that the wear of the kneader, the molding machine and the mold becomes severe.
Therefore, magnesium oxide having a thermal conductivity that is an order of magnitude higher than that of silica and about the same thermal conductivity as alumina has been studied as a material for resin fillers for semiconductor encapsulation. However, the magnesium oxide powder has higher hygroscopicity than the silica powder. For this reason, when magnesium oxide powder is used as a resin filler for semiconductor encapsulation, the absorbed water and magnesium oxide are hydrated, causing problems such as cracks due to volume expansion of the filler and reduced thermal conductivity. It was. For this reason, providing moisture resistance to the magnesium oxide powder used as the resin filler for semiconductor encapsulation has been a major issue in ensuring long-term stable operation of the semiconductor.
As a method for improving the moisture resistance of magnesium oxide powder, Japanese Patent Application Laid-Open No. 2003-34522 and Japanese Patent Application Laid-Open No. 2003-34523 include mixing an aluminum salt or a silicon compound and magnesium oxide powder, and filtering off a solid content. A method for producing a coated magnesium oxide powder is disclosed, wherein the surface of the magnesium oxide powder is coated with a coating layer containing aluminum or a double oxide of silicon and magnesium by drying and firing. .
Although the coated magnesium oxide powder obtained by these methods has improved moisture resistance, since the powder particles have an angular shape, the resin filling property is low, and the fluidity of the resulting resin composition There is a problem that is low.
On the other hand, in Japanese Patent No. 2590491, alumina particles and / or silica particles are added to a magnesium oxide powder and granulated using a spray dryer to obtain spherical granules, and then the granulated state is destroyed. There is also disclosed a method for producing a magnesium oxide-based material in which at least a part of the granulated material is melted and then rapidly cooled.
This method is intended to improve the moisture resistance of the magnesium oxide particles. However, since it is granulated using a spray dryer, the resulting spherical granule is an aggregate of particles, that is, a porous body, and is highly resistant to resin. It can be expected to be difficult to fill.
An object of the present invention is to provide a coated magnesium oxide powder that solves the above-mentioned problems, has excellent moisture resistance, has excellent filling properties when used as a filler, and can be highly filled into a resin. Another object of the present invention is to provide a resin composition excellent in moisture resistance, thermal conductivity and fluidity, containing the coated magnesium oxide powder, and an electronic device using the resin composition.

In order to achieve the above object, the present inventor has made various studies, paying attention to the angle of repose as the parameter indicating the fluidity of the powder and the tap density as the parameter indicating the filling property, and specifying each value It was found that a powder excellent in fluidity and filling property can be obtained when the amount is within the range of the above, and a resin composition excellent in fluidity can be obtained using the powder.
That is, according to the present invention, there is provided a coated magnesium oxide powder having a surface coated with a double oxide, an angle of repose of 55 degrees or less, and a tap density of 1.65 g / ml or more.
Moreover, according to this invention, the electronic device using the resin composition containing said coating magnesium oxide powder as a filler and the resin composition is provided.

Coated magnesium oxide powder The coated magnesium oxide powder in the present invention has a surface coated with a double oxide, an angle of repose of 55 degrees or less, and a tap density of 1.65 g / ml or more.
Here, the angle of repose is R.I. L. It is one of the characteristic values for calculating the flowability index of the powder proposed by Carr, that is, the so-called Carr's flowability index, and the flowability of the powder can be evaluated by the angle of repose. it can. Specifically, it refers to the angle formed between the generatrix and the horizontal plane formed when the powder is gently dropped onto a horizontal surface using a funnel.
By setting the angle of repose to 55 degrees or less, the fluidity of the powder is improved, and as a result, the fluidity of the resin composition containing the powder can be improved. The angle of repose is preferably 50 degrees or less.
The tap density is an index for evaluating the filling property of the powder, and means the powder mass per unit volume when a powder sample is put in a container having a known volume and tapped a predetermined number of times from a certain height. This tapping density is 1.65 g / ml or more, and more preferably 1.80 g / ml or more.
The surface of the coated magnesium oxide powder of the present invention is coated with a double oxide. The double oxide covering the surface of the magnesium oxide powder preferably contains one or more elements selected from the group consisting of aluminum, iron, silicon and titanium and magnesium. By covering the surface with this double oxide, the moisture resistance of the magnesium oxide powder is greatly improved.
Examples of the double oxide include forsterite (Mg ₂ SiO ₄ ), spinel (Al ₂ MgO ₄ ), magnesium ferrite (Fe ₂ MgO ₄ ), magnesium titanate (MgTiO ₃ ), and the like.
The content of the double oxide used in the present invention, that is, the ratio of the surface double oxide to one particle is preferably 5 to 50 mass%, more preferably 10 to 40 mass%. When the content of the double oxide is in the above range, the surface of the magnesium oxide powder is completely covered with the double oxide, and the moisture resistance is greatly improved. Furthermore, the thermal conductivity of the resin composition after filling is further improved. In other words, it can exhibit a sufficient effect as a thermally conductive filler.
The average particle diameter of the coated magnesium oxide powder of the present invention is preferably ^{5 × 10 -6 ~500 × 10 -6} m, more preferably ^{10 × 10 -6 ~100 × 10- 6} m. Further, the BET specific surface area is preferably 5.0 × 10 ³ m ² / kg or less, and more preferably 1 × 10 ³ m ² / kg or less.
The coated magnesium oxide powder having an angle of repose of 55 degrees or less and a tap density of 1.65 g / ml or more according to the present invention is melted at a high temperature in the presence of a compound that forms a double oxide on the surface of the magnesium oxide powder. Thus, the coated magnesium oxide powder can be produced by spheronizing. For example, the powder is melted by passing through a high-temperature flame and spheroidized by surface tension.
Moreover, it is also possible to manufacture by firing at a firing temperature not higher than the melting point of the coating material in a state where a compound that forms a double oxide is present on the surface of the magnesium oxide powder. Since the coated magnesium oxide powder obtained by this method is not necessarily spherical, a powder satisfying the fluidity index and the oil absorption amount of the present invention is produced by mixing powders having different particle sizes.
The compound used to form the double oxide is preferably one or more compounds selected from the group consisting of aluminum compounds, iron compounds, silicon compounds and titanium compounds. The form of the compound is not limited, but nitrate, sulfate, chloride, oxynitrate, oxysulfate, oxychloride, hydroxide, and oxide are used.
The compounding amount of these compounds with respect to the magnesium oxide powder is preferably determined such that the content of the double oxide in the finally obtained coated magnesium oxide powder is 5 to 50 mass%.
The crystallite diameter of the magnesium oxide powder used in the present invention is preferably 50 × 10 ⁻⁹ m or more. Magnesium oxide powder having a crystallite size of 50 × 10 ⁻⁹ m or more is less reactive than finer powder and can uniformly adsorb silicon compounds and the like on the surface of magnesium oxide powder. The double oxide covering the surface of the magnesium powder becomes uniform, and the water resistance is improved.
The crystallite diameter used in the present invention is a value calculated by the Scherrer equation using the X-ray diffraction method. In general, one particle is a polycrystal composed of a plurality of single crystals, and the crystallite diameter indicates an average value of the sizes of the single crystals in the polycrystal.
The purity of the magnesium oxide powder is not particularly limited, and is preferably determined according to the application. For example, in order to satisfy the insulation characteristics of the electronic component, the purity is preferably 90% or more, and more preferably 95% or more. The magnesium oxide powder having the characteristics of the present invention can be produced using a known method such as an electrofusion method or a sintering method.
Resin Composition Containing Coated Magnesium Oxide Powder By the above production method, a coated magnesium oxide powder having a high filling property to the resin can be easily obtained at low cost while maintaining moisture resistance and thermal conductivity. Moreover, the resin composition filled with the coated magnesium oxide powder thus obtained has good fluidity and improved moldability.
The resin composition of the present invention is obtained by containing the above-mentioned coated magnesium oxide powder in a resin.
In that case, the coated magnesium oxide powder of the present invention can be surface-treated with a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent, if necessary, to further improve the filling property. it can.
Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrialkoxysilane, glycidoxypropyltrialkoxysilane, methacryloxypropylmethyl dialkoxysilane, and the like.
Examples of titanate coupling agents include isopropyl triisostearoyl titanate, tetraoctyl bis (ditridecyl phosphite) titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, and the like.
The resin used in the resin composition of the present invention is not particularly limited, and is a thermosetting resin such as an epoxy resin, a phenol resin, a polyimide resin, a polyester resin, or a silicone resin, a polycarbonate resin, an acrylic resin, a polyphenylene sulfide resin, a fluorine resin, or the like. And other thermoplastic resins. Of these, epoxy resins, silicone resins, and polyphenylene sulfide resins are preferred. Moreover, a hardening | curing agent and a hardening accelerator can be mix | blended as needed.
Examples of the epoxy resin include bisphenol A epoxy resin, novolak type epoxy resin, bisphenol F epoxy resin, brominated epoxy resin, orthocresol novolak type epoxy resin, glycidyl ester resin, glycidyl amine resin, heterocyclic epoxy resin, and the like. It is done.
Examples of the phenol resin include novolac type phenol resins and resol type phenol resins.
Examples of the silicone resin include millable type silicone rubber, condensation type liquid silicone rubber, addition type liquid silicone rubber, UV curable type silicone rubber, and the like, and addition type liquid silicone rubber is preferable. Either one-pack type or two-pack type silicone rubber may be used, but two-pack type silicone rubber is preferred.
In addition to the above-mentioned coated magnesium oxide powder, a filler can be blended in the resin composition of the present invention. The filler is not particularly limited, and examples thereof include fused silica and crystalline silica. Moreover, a mold release agent, a flame retardant, a coloring agent, a low stress imparting agent, etc. can be suitably mix | blended as needed.
The electronic device of the present invention uses the above resin composition as a part thereof, and has excellent heat dissipation and moisture resistance. Examples of the electronic device include a resin circuit board, a metal base circuit board, a metal-clad laminate, a metal-clad laminate with an inner layer circuit, and the like.
Examples of the use of the resin composition of the present invention for the above-described electronic device include a semiconductor sealing agent, an adhesive or an adhesive sheet, a heat dissipation sheet, a heat dissipation spacer, or a heat dissipation grease.
In order to produce the above-mentioned substrate or the like using the resin composition of the present invention, a paper base material or a glass base material is immersed in the resin composition of the present invention, dried by heating and cured to the B stage, and a prepreg ( Resin cloth, resin paper, etc.).
Moreover, a resin circuit board, a metal-clad laminate, a metal-clad laminate with an inner layer circuit, etc. can be produced using this prepreg. For example, for metal-clad laminates, prepregs are stacked according to the substrate thickness, metal foil is placed, sandwiched between molds, inserted between the hot plates of a press machine, and the laminates are formed by predetermined heating and pressing. Further, the four sides of the formed laminated board are cut and manufactured by performing an appearance inspection.
In addition, the resin composition of the present invention can be mixed with other base material and used as a base material in the form of a composite material such as glass epoxy and Teflon epoxy.
The resin composition of the present invention can be used as a sealing material. The sealing resin is a resin material used for packaging to protect a semiconductor chip from external factors such as mechanical, thermal stress, humidity, etc., and is formed by the resin composition of the present invention. The performance of the package is indicated by the thermal conductivity and weather resistance of the cured resin.
The resin composition of the present invention can be used as an adhesive. The adhesive refers to a substance used for bonding two objects together, and the material of the adherend is not particularly limited. The adhesive is temporarily given fluidity when applied or engaged with the surface of the adherend, and loses fluidity and solidifies after adhesion. Examples thereof include solvent adhesives, pressure sensitive adhesives, heat sensitive adhesives such as adhesive sheets, and reactive adhesives. When the resin composition of the present invention is used as an adhesive, the thermal conductivity and weather resistance after adhesion are indicated by the thermal conductivity and weather resistance of the resin cured product.
Moreover, a metal base circuit board can be manufactured using the resin composition of this invention as an adhesive agent. The metal base circuit board is manufactured by applying an adhesive on a metal plate, laminating a metal foil when the adhesive is in a B-stage state, performing predetermined heating and pressing, and integrating them.
Moreover, the resin composition of this invention can be used as a heat dissipation material. Examples of the heat radiating material include a heat radiating sheet, a heat radiating spacer, and a heat radiating grease. A heat dissipation sheet is an electrically insulating heat conductive sheet for removing heat generated from heat-generating electronic components and electronic devices, and is manufactured by filling a silicone rubber with a heat conductive filler. Used by attaching to a plate. The heat dissipating grease is the same as the heat dissipating sheet except that silicone oil is used instead of silicone rubber. The heat dissipation spacer is a solidified silicone with a thickness that fills the space between the exothermic electronic component and the electronic device to transfer the heat generated from the exothermic electronic component and electronic device directly to the case of the electronic device. It is a thing.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.
1. Coated magnesium oxide powder synthesis example 1
Magnesium oxide powder (KMAO-H manufactured by Tateho Chemical Industry Co., Ltd.), which is an aggregate of single crystals having a crystallite size of 58.3 × 10 ⁻⁹ m, was used in an impact pulverizer to obtain a particle size of 100 × 10 ⁻ It grind | pulverized to ⁶ m or less. Fumed silica (purity 99.9% or more, specific surface area 200 ± 20 m ² / g) was wet-added so that the mixing ratio was 10 mass% with respect to magnesium oxide, and stirred and mixed at 400 to 500 rpm for 600 s. After stirring and mixing, the cake obtained by filtration and dehydration was dried overnight at 423 K using a dryer. The dried cake was crushed with a sample mill and adjusted to a particle size comparable to that of the raw material magnesium oxide powder to obtain a coated magnesium oxide powder.
Synthesis example 2
Magnesium oxide powder (KMAO-H, manufactured by Tateho Chemical Industry Co., Ltd.), which is an aggregate of single crystals having a crystallite size of 58.3 × 10 ⁻⁹ m, was used in an impact pulverizer to obtain a particle size of 7 × 10 ⁻ It grind | pulverized to ⁶ m or less. Fumed silica (purity 99.9% or more, specific surface area 200 ± 20 m ² / g) was wet-added so that the mixing ratio was 10 mass% with respect to magnesium oxide, and stirred and mixed at 400 to 500 rpm for 600 s. After stirring and mixing, the cake obtained by filtration and dehydration was dried overnight at 423 K using a dryer. The dried cake was crushed with a sample mill and adjusted to a particle size comparable to that of the raw material magnesium oxide powder to obtain a coated magnesium oxide powder.
Synthesis example 3
A coated magnesium oxide powder was obtained in the same manner as in Synthesis Example 1 except that the mixing ratio of fumed silica was changed to 3 mass%.
Synthesis example 4
A coated magnesium oxide powder was obtained in the same manner as in Synthesis Example 1 except that the mixing ratio of fumed silica was changed to 30 mass%.
Synthesis example 5
Magnesium oxide powder (KMAO-H manufactured by Tateho Chemical Industry Co., Ltd.), which is an aggregate of single crystals having a crystallite size of 58.3 × 10 ⁻⁹ m, was used in an impact pulverizer to obtain a particle size of 100 × 10 ⁻ It grind | pulverized to ⁶ m or less. 4% aluminum nitrate aqueous solution (special grade reagent manufactured by Kanto Chemical Co., Inc.) is added in a wet manner so that the mixing ratio is 10 mass% with respect to magnesium oxide in terms of Al ₂ O _3, and is stirred and mixed at 400 to 500 rpm for 600 s. did. After stirring and mixing, the mixture was filtered and a cake started to be formed. To remove residual aluminum nitrate, the cake was sufficiently washed with water and dehydrated, and dried at 423 K overnight using a dryer. The dried cake was crushed with a sample mill and adjusted to a particle size comparable to that of the raw material magnesium oxide powder to obtain a coated magnesium oxide powder.
Synthesis Example 6
In place of aluminum nitrate, an iron nitrate aqueous solution was converted into Fe ₂ O ₃ , and was mixed in the same manner as in Synthesis Example 4 except that the mixing ratio was 15 mass% with respect to magnesium oxide. Magnesium powder was obtained.

The powder produced in Synthesis Example 1 is supplied into a high-temperature flame formed by burning liquefied propane gas and oxygen, melted and spheroidized, and coated with forsterite (Mg ₂ SiO ₄ ). Magnesium powder was obtained.

The powder produced in Synthesis Example 1 was fired in air at 1723 K for 3600 s, then pulverized again with a sample mill, adjusted to a particle size comparable to that of the raw material magnesium oxide powder, and forsterite (Mg ₂ SiO ₂ A coated magnesium oxide powder coated with ₄ ) was obtained.
On the other hand, the powder produced in Synthesis Example 2 was treated in the same manner as described above to adjust the particle size to the same level as that of the raw material magnesium oxide powder and coated with forsterite (Mg ₂ SiO ₄ ). Got.
The coated magnesium oxide powder obtained from Synthesis Example 1 and the coated magnesium oxide powder obtained from Synthesis Example 2 were mixed at a mass ratio of 7: 3.

A spherical coated magnesium oxide powder coated with forsterite (Mg ₂ SiO ₄ ) was obtained in the same manner as in Example 1 except that the powder prepared in Synthesis Example 3 was used.

A spherical coated magnesium oxide powder coated with forsterite (Mg ₂ SiO ₄ ) was obtained in the same manner as in Example 1 except that the powder produced in Synthesis Example 4 was used.

A spherical coated magnesium oxide powder coated with spinel (Al ₂ MgO ₄ ) was obtained in the same manner as in Example 1 except that the powder prepared in Synthesis Example 5 was used.

２．樹脂組成物A spherical coated magnesium oxide powder coated with magnesium ferrite (Fe ₂ MgO ₄ ) was obtained in the same manner as in Example 1 except that the powder prepared in Synthesis Example 6 was used.
Comparative Example 1
The powder obtained in Synthesis Example 1 was calcined in air at 1723 K for 3600 s, and then pulverized again with a sample mill to adjust the particle size to the same level as that of the raw material magnesium oxide powder. A coated magnesium oxide powder coated with ₂ SiO ₄ ) was obtained.
Comparative Example 2
Magnesium oxide powder was supplied into a high-temperature flame formed by combustion of liquefied propane gas and oxygen to obtain a magnesium oxide powder whose surface was not coated.
Evaluation Test Content of coated double oxide, angle of repose, tap density, BET specific surface area, average particle diameter and moisture resistance of the coated magnesium oxide powder samples obtained in the above Examples 1 to 6 and Comparative Examples 1 and 2 Each item was measured and the results are shown in Table 1. In addition, the measuring method of each item is shown below.
Content of double oxide on powder surface: Using a scanning X-ray fluorescence analyzer “ZSX-100e” (manufactured by Rigaku Denki Kogyo Co., Ltd.), the content of elements contained in the powder sample was measured, and the double oxide was measured. It converted into content of.
Angle of repose: Using a powder physical property measuring device “Powder Tester PT-N” (manufactured by Hosokawa Micron Corporation), a standard sieve (mesh 710 μm) is vibrated, and a powder sample is dropped through a funnel. ) Was measured.
Tap density: After using a powder physical property measuring apparatus “Powder Tester PT-N” (manufactured by Hosokawa Micron Corporation), a powder sample is put into a 100 ml container, tapped 180 times from a certain height, and hardened by impact of tapping. The tapping density (g / ml) was measured.
BET specific surface area: The specific surface area of the powder sample was measured by a gas adsorption method using a flow-type specific surface area measuring apparatus “Flowsorb II2300” (manufactured by Shimadzu Corporation).
Average particle diameter: The volume average particle diameter of the powder sample was measured by a particle size distribution measuring apparatus “Microtrac HRA” (manufactured by Nikkiso Co., Ltd.) by a laser diffraction / scattering method.
Moisture resistance test: The obtained sample 5 × 10 ⁻³ kg was stirred in boiling water 100 × 10 ⁻⁶ m ³ at a temperature of 373 K for 2 hours, and the mass increase rate was measured to evaluate the moisture resistance.

2. Resin composition

To the sample powder prepared in Example 1, 1.0 mass% of epoxysilane was added, and the powder was surface-treated by stirring and mixing for 600 s, and then dried at 423 K for 7200 s. 560 parts by weight of the obtained sample was mixed with 63 parts by weight of an orthocresol novolac type epoxy resin, 34 parts by weight of a novolac type phenolic resin, 1 part by weight of triphenylphosphine and 2 parts by weight of carnauba wax using a crusher for 600 s. Crushed. Thereafter, the mixture was kneaded at 373 K for 300 s using a two-roll, and then this kneaded material was further pulverized to 10 mesh or less to produce φ38 mm × t15 mm pellets. This pellet was transfer-molded at 7 MPa and 448 K for 180 s, and the spiral flow was measured.
Further, this pellet was transfer-molded at 448K for 180 s and 7 MPa, and then post-cured for 18 × 10 ³ s at 453K to obtain a molded body of φ50 mm × t3 mm.

  Spiral flow was measured in the same manner as in Example 7 except that a mixed powder of coated magnesium oxide powders having different particle diameters produced in Example 2 was used to obtain a molded body.

  Except that the spherical coated magnesium oxide powder produced in Example 3 was used, spiral flow was measured in the same manner as in Example 6 to obtain a molded body.

  Except that the spherical coated magnesium oxide powder produced in Example 4 was used, spiral flow was measured in the same manner as in Example 6 to obtain a molded body.

  Except that the spherical coated magnesium oxide powder prepared in Example 5 was used, spiral flow was measured in the same manner as in Example 6 to obtain a molded body.

Except that the spherical coated magnesium oxide powder produced in Example 6 was used, spiral flow was measured in the same manner as in Example 6 to obtain a molded body.
Comparative Example 3
Except that the sample prepared in Comparative Example 1 was used, spiral flow was measured in the same manner as in Example 7 to obtain a molded body.
Comparative Example 4
A spiral flow was measured in the same manner as in Example 7 except that alumina powder was used in place of the magnesium oxide powder to obtain a molded body.

  1.0 mass% of vinyltrimethoxysilane was added to the sample powder prepared in Example 1, and the powder was surface-treated by stirring and mixing for 600 s, and then dried at 423 K for 7200 s. 451 parts by weight of the obtained sample was kneaded for 300 s using 100 parts by weight of a two-component RTV silicone rubber and two rolls. Next, 5 parts by weight of a platinum catalyst was added and kneaded for 600 s using a two-roll, to prepare a compound, and the viscosity was measured under the following conditions. This was press-molded at 393 K for 600 s and 5 MPa to obtain a molded body of φ50 mm × t3 mm.

以上の結果から明らかなように、本発明の安息角及びタップ密度を共に満足する被覆酸化マグネシウム粉末は、球状化処理を施したもの（表１、実施例１、３〜６）及び焼成により得られた粉末を混合して得られたもの（表１、実施例２）共に、耐湿性に優れている。そして、これらの粉末を充填してなる樹脂組成物（表２、実施例７〜１４）は、流動性に優れており、さらに、その成型体は高い熱伝導率を有し、耐湿性に優れていることが確認された。
一方、比較例１の粉末は、耐湿性は優れていたが、タップ密度が本発明の範囲を下回っている。これをエポキシ樹脂に充填した場合（表２、比較例３）、及びシリコーンゴムに充填した場合（表２、比較例５）共に、流動性が低い値となった。
比較例２の粉末は複酸化物で被覆されていないので、表１に示したように耐湿性が非常に低いものであった
また、酸化マグネシウム粉末に代えて、従来のアルミナ粉末を充填して得られた樹脂組成物（表２、比較例４，６）は、流動性及び耐湿性は優れているものの、熱伝導性に劣っていた。Except for using the mixed sample powder prepared in Example 2, the viscosity was measured in the same manner as in Example 13 to obtain a molded body.
Comparative Example 5
Except for using the sample powder prepared in Comparative Example 1, the viscosity was measured in the same manner as in Example 13 to obtain a molded body.
Comparative Example 6
Viscosity was measured in the same manner as in Example 13 except that alumina powder was used instead of magnesium oxide powder to obtain a molded body.
Evaluation Test Spiral flow or viscosity of resin compositions obtained in the above Examples 7 to 14 and Comparative Examples 3 to 6 (an appropriate measurement method was selected depending on the state of the resin at room temperature), and these resins The appearance of the molded body of the composition after the thermal conductivity, moisture resistance and moisture resistance test was measured, and the results are shown in Table 2. In addition, the evaluation method of said each item is as follows.
Spiral flow: Measured according to EMMI-I-66.
Viscosity: The viscosity was measured using a rheometer “VAR-50” (manufactured by REOLOGICA), and the shear rate was 1 s ⁻¹ .
Thermal conductivity: The thermal conductivity of the molded body was measured by a laser flash method using a thermal constant measuring device “TC-3000” (manufactured by Vacuum Riko Co., Ltd.).
Humidity resistance test: The molded body was stored for 7 days in a thermo-hygrostat set to a temperature of 358K and a humidity of 85%, and the moisture absorption rate was measured. The appearance was visually observed.

As is clear from the above results, the coated magnesium oxide powder satisfying both the angle of repose and the tap density of the present invention was obtained by spheroidizing treatment (Table 1, Examples 1 and 3 to 6) and firing. Both those obtained by mixing the obtained powder (Table 1, Example 2) are excellent in moisture resistance. And the resin composition (Table 2, Examples 7-14) formed by filling these powders is excellent in fluidity | liquidity, Furthermore, the molded object has high heat conductivity, and is excellent in moisture resistance. It was confirmed that
On the other hand, the powder of Comparative Example 1 was excellent in moisture resistance, but the tap density was below the range of the present invention. When the epoxy resin was filled (Table 2, Comparative Example 3) and when the silicone rubber was filled (Table 2, Comparative Example 5), the fluidity was low.
Since the powder of Comparative Example 2 was not coated with the double oxide, the moisture resistance was very low as shown in Table 1. Also, instead of the magnesium oxide powder, the conventional alumina powder was filled. Although the obtained resin composition (Table 2, Comparative Examples 4 and 6) was excellent in fluidity and moisture resistance, it was inferior in thermal conductivity.

As described above in detail, the coated magnesium oxide powder of the present invention is excellent in moisture resistance and, when used as a filler, is excellent in filling properties, can be highly filled into a resin, and is useful as a heat conductive filler. is there.
In addition, the resin composition obtained by filling this coated magnesium oxide powder has excellent fluidity, and the molded body has high heat dissipation and moisture resistance, so that it can be used as a sealing material or spacer for various electronic devices. It is very useful as a component such as an adhesive or an adhesive sheet, or a resin circuit board, a metal base circuit board, a metal-clad laminate, a metal-clad laminate with an inner layer circuit, and its industrial value is extremely high.

Claims (8)

A coated magnesium oxide powder having a surface coated with a double oxide, an angle of repose of 55 degrees or less, and a tap density of 1.65 g / ml or more. The coated magnesium oxide powder according to claim 1, wherein the double oxide contains one or more elements selected from the group consisting of aluminum, iron, silicon, and titanium and magnesium. The coated magnesium oxide powder according to claim 1 or 2, wherein the mixed oxide contains 5 to 50 mass%. The coating oxidation according to any one of claims 1 to 3, wherein the average particle diameter is 5 x 10 ^{-6 to} 500 x 10 ^-6 m and the BET specific surface area is 5 x 10 ³ m ² / kg or less. Magnesium powder. The resin composition containing the covering magnesium oxide powder of any one of Claims 1-4. The resin composition according to claim 5, wherein the resin of the resin composition is an epoxy resin. The resin composition according to claim 5, wherein the resin of the resin composition is silicone rubber. The electronic device using the resin composition of any one of Claims 5-7.