JP2008258253A - Material excellent in electromagnetic wave shielding property and heat dissipation and molded good - Google Patents
Material excellent in electromagnetic wave shielding property and heat dissipation and molded good Download PDFInfo
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- 229910052582 BN Inorganic materials 0.000 claims abstract description 6
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- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 6
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 6
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 5
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Abstract
Description
本発明は、電磁波遮蔽性と放熱性に優れた材料に関する。特に1MHzから1GHzを越える広帯域での電磁波を遮蔽できる材料に関する。 The present invention relates to a material excellent in electromagnetic wave shielding and heat dissipation. In particular, the present invention relates to a material capable of shielding electromagnetic waves in a wide band exceeding 1 MHz to 1 GHz.
電子機器の分野において、発熱素子の放熱は重要な課題である。また誤動作の原因となるため、機器や素子を電磁波から保護することも強く求められている。 In the field of electronic equipment, heat dissipation of the heating element is an important issue. Moreover, since it causes malfunctioning, it is strongly required to protect devices and elements from electromagnetic waves.
発熱素子の放熱に関しては、例えば熱伝導性に優れた銅若しくはアルミからなるヒートシンクが用いられている。また、発熱素子の実温度上昇と共に、ヒートシンク以外にも、内部に冷却液を装填したヒートパイプを用いることが増加してきている。しかし、上述した銅やアルミ等の金属製のヒートシンクにおいて、放熱性を向上させる場合には、ヒートシンクのフィンを薄くし背を高くする必要がある。この際に渦電流が発生しやすく別途電磁波シールドを行う必要があり、電子機器のコストアップと薄型化を阻む要因となっている。
また、金属の放熱材料は比重が大きいために軽量化を阻む要因ともなっている。さらに、金属製のヒートシンクは熱伝導性が高く、発熱素子の熱を移動させやすい特徴がある一方、自己放熱性に乏しく、熱を吸収してもそれを放熱しにくいため、発熱素子を冷却させる際には冷却ファンを用いて常にこれら金属製のヒートシンクの表面を冷却させる必要がある。
For heat dissipation of the heat generating element, for example, a heat sink made of copper or aluminum having excellent thermal conductivity is used. Further, as the actual temperature of the heat generating element rises, the use of heat pipes loaded with a cooling liquid is increasing in addition to the heat sink. However, in the above-described heat sink made of metal such as copper or aluminum, it is necessary to make the fin of the heat sink thinner and taller in order to improve heat dissipation. At this time, an eddy current is likely to be generated, and it is necessary to separately shield an electromagnetic wave, which is a factor that hinders the cost increase and thinning of the electronic device.
In addition, since the metal heat dissipation material has a large specific gravity, it is a factor that hinders weight reduction. In addition, the heat sink made of metal has high thermal conductivity and is easy to move the heat of the heating element. On the other hand, the heat sink is cooled because it is not self-dissipating and it is difficult to dissipate heat even if it absorbs heat. In some cases, it is always necessary to cool the surface of these metal heat sinks using a cooling fan.
電磁波を遮蔽する電磁波シールド体としては、通常、金属の板、箔、メッシュ、導電性の皮膜、導電性充填剤を混入した複合材、メッキ、蒸着、塗装等による導電性表面処理物が使用されている。
従来、放熱用の部材と電磁波遮蔽用の部材には別のものが用いられていたため、コストが割高になり、製品の薄型化にも支障を来していた。
As electromagnetic wave shielding bodies for shielding electromagnetic waves, metal plates, foils, meshes, conductive films, composite materials mixed with conductive fillers, conductive surface treated products such as plating, vapor deposition, and painting are usually used. ing.
Conventionally, separate members have been used for the heat radiation member and the electromagnetic wave shielding member, which has increased the cost and hindered the thickness reduction of the product.
上述した問題を解決するために、電磁波をシールドするとともに、熱伝導性に優れた材料を提供する技術もいくつか見られる。例えば、特許文献1及び特許文献2では、導電性層と絶縁性層および電磁波シールド層からなる多層構造のシートが提案されている。また、特許文献3では樹脂にフェライト粉末及びカーボンナノチューブを少量添加し、熱伝導性と静電気除去効果に優れた熱伝導シートが提案されている。 In order to solve the above-described problems, there are some techniques that shield electromagnetic waves and provide materials having excellent thermal conductivity. For example, Patent Document 1 and Patent Document 2 propose a sheet having a multilayer structure including a conductive layer, an insulating layer, and an electromagnetic wave shielding layer. Further, Patent Document 3 proposes a heat conductive sheet in which a small amount of ferrite powder and carbon nanotubes are added to a resin and excellent in heat conductivity and static electricity removing effect.
しかし、特許文献1および2のシートでは、多層シートを構成させるために、それぞれの層の密着性が問題となり、少しでも剥離箇所があると、特性が急激に落ちる問題がある。また、それぞれの層を別々に作る必要があるため、肉厚を薄くすることが難しいと共に、複雑形状の製品を作ることが困難であるという問題がある。また、それぞれの層を組み合わせて作る必要があるため、コストアップの要因になる。また、これらシートにおいては金属を用いているため、自己放熱性に乏しく、ヒートシンクとの併用が一般的である。また、電磁波をシールドする性質は有するものの、電磁波を吸収する性質は有しないため、筐体の内面の全面に金属材料による導電性表面処理を行う必要があり、コストアップの要因となる。
一方、特許文献3のシートは多層構造を取っていないが、熱伝導率は5W/m・K以下と、ヒートシンクとして使用できるほどの値は示しておらず、放熱効果は十分とは言えない。
On the other hand, although the sheet of Patent Document 3 does not have a multilayer structure, the thermal conductivity is 5 W / m · K or less, which does not indicate a value that can be used as a heat sink, and the heat dissipation effect is not sufficient.
また、電磁波の遮蔽に関しては広帯域での遮蔽特性が求められているが、特定の周波数で遮蔽性を示す材料は多くあるものの、1MHzから1GHzを越えるような広帯域での遮蔽特性を示す材料を見いだすことは容易ではなく、熱を下げる効果に優れるともに、広帯域での電磁波遮蔽性を示す材料が求められていた。 In addition, for shielding electromagnetic waves, there is a demand for shielding characteristics in a wide band. However, although there are many materials that exhibit shielding properties at specific frequencies, a material that exhibits shielding characteristics in a wide band that exceeds 1 MHz to 1 GHz is found. This is not easy, and there has been a demand for a material that is excellent in the effect of lowering heat and exhibits electromagnetic wave shielding properties in a wide band.
したがって本発明は、放熱性および電磁波遮蔽性に優れた材料、特に1MHzから1GHzを越えるような広帯域で優れたシールド特性を示す材料を提供することを課題とする。 Therefore, an object of the present invention is to provide a material excellent in heat dissipation and electromagnetic wave shielding properties, particularly a material exhibiting excellent shielding characteristics in a wide band exceeding 1 MHz to 1 GHz.
本発明者らは、前記課題を解決するために様々な検討を行った結果、特定のセラミックス粉末と炭素繊維を樹脂に均一に混合することによって、放熱性に優れるとともに、広帯域の電磁波を遮蔽する材料を製造することに成功し、前記課題を解決した。 As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have excellent heat dissipation and shield broadband electromagnetic waves by uniformly mixing a specific ceramic powder and carbon fiber with a resin. We succeeded in manufacturing the material and solved the above problems.
すなわち本発明は、放熱性と電磁波遮蔽性を有する材料であって、樹脂中に、セラミックス粉末と炭素繊維が均一に分散されていること、および前記セラミックス粉末が、アルミナ粉末、窒化アルミ粉末、炭化珪素粉末、窒化珪素粉末および窒化硼素粉末からなる群から選択され、前記炭素繊維が、ピッチ系炭素繊維、ピッチ系超高弾性率炭素繊維およびカーボンナノチューブからなる群から選択されることを特徴とする。 That is, the present invention is a material having heat dissipation and electromagnetic wave shielding properties, wherein ceramic powder and carbon fiber are uniformly dispersed in a resin, and the ceramic powder is made of alumina powder, aluminum nitride powder, carbonized carbon. It is selected from the group consisting of silicon powder, silicon nitride powder and boron nitride powder, and the carbon fiber is selected from the group consisting of pitch-based carbon fiber, pitch-based ultrahigh modulus carbon fiber and carbon nanotube. .
セラミックスは金属と異なり、自己放熱性を有しており、また、熱膨張係数が小さいという特徴が有る。カーボンは、熱伝導性と電磁波吸収性を有する。セラミックスとしてアルミナ、窒化アルミ、炭化珪素、窒化珪素、窒化硼素粉末を採用し、炭素繊維としてピッチ系炭素繊維、ピッチ系超高弾性率炭素繊維、カーボンナノチューブを採用し、両者を樹脂に均一に分散させることにより、良好な放熱性と電磁波吸収性を併せ持つ材料を得ることができる。また、炭素繊維は、セラミックス粉末の隙間に均一に分散し、セラミックス粉末表面に炭素繊維の一部が接し、炭素繊維同士が絡み合う事により放熱性がさらに高められる。 Ceramics, unlike metals, have a feature of self-heat dissipation and a low coefficient of thermal expansion. Carbon has thermal conductivity and electromagnetic wave absorption. Alumina, aluminum nitride, silicon carbide, silicon nitride, and boron nitride powder are used as ceramics, and pitch-based carbon fibers, pitch-based ultrahigh modulus carbon fibers, and carbon nanotubes are used as carbon fibers, and both are uniformly dispersed in the resin. By doing so, a material having both good heat dissipation and electromagnetic wave absorption can be obtained. Further, the carbon fibers are uniformly dispersed in the gaps between the ceramic powders, part of the carbon fibers are in contact with the surface of the ceramic powders, and the carbon fibers are entangled with each other, thereby further improving the heat dissipation.
本発明にかかる材料は、放熱性および電磁波遮蔽性の両方に優れており、特に広帯域で良好な電磁波遮蔽特性を示すことができる。 The material according to the present invention is excellent in both heat dissipation and electromagnetic wave shielding properties, and can exhibit good electromagnetic wave shielding characteristics particularly in a wide band.
本発明に用いられる樹脂は、熱可塑性樹脂及び熱硬化性樹脂の何れでもよく、熱可塑性樹脂ではポリオレフィン系樹脂、ポリアミド系樹脂、エラストマー系(スチレン系,オレフィン系,PVC系,ウレタン系,エステル系,アミド系)樹脂、アクリル系樹脂、エンジニアリングプラスチック等が用いられる。特にポリエチレン、ポリプロピレン、ナイロン樹脂、ABS樹脂、アクリル樹脂、エチレンアクリレート樹脂、エチレン酢酸ビニル樹脂、ポリスチレン樹脂、ポリフェニレンサルファイド樹脂、ポリカーボネート樹脂、ポリエステルエラストマー樹脂、ポリアミドエラストマー樹脂、液晶ポリマーが選ばれる。中でも耐熱性及び柔軟性からナイロン樹脂、ポリエステルエラストマー樹脂、ポリアミドエラストマー樹脂、ABS樹脂、ポリプロピレン樹脂、ポリフェニレンサルファイド樹脂、液晶ポリマーが好適である。
また、熱硬化性樹脂にはエポキシ樹脂、メラミン樹脂、フェノール樹脂、シリコーン樹脂、ウレタン樹脂等が用いられる。なかでも、耐熱性及び柔軟性からエポキシ樹脂、シリコーン樹脂及びウレタン樹脂が好適である。
これら樹脂には分散剤、潤滑剤、可塑剤を添加してもよく、とくに分散剤に脂肪酸系エステルを用いる事により、セラミックス、及び炭素繊維材料の充填率を増加させ、特性を向上することができる。
The resin used in the present invention may be either a thermoplastic resin or a thermosetting resin. In the thermoplastic resin, a polyolefin resin, a polyamide resin, an elastomer (styrene, olefin, PVC, urethane, ester) , Amide-based) resin, acrylic resin, engineering plastic, etc. are used. In particular, polyethylene, polypropylene, nylon resin, ABS resin, acrylic resin, ethylene acrylate resin, ethylene vinyl acetate resin, polystyrene resin, polyphenylene sulfide resin, polycarbonate resin, polyester elastomer resin, polyamide elastomer resin, and liquid crystal polymer are selected. Among these, nylon resin, polyester elastomer resin, polyamide elastomer resin, ABS resin, polypropylene resin, polyphenylene sulfide resin, and liquid crystal polymer are preferable because of heat resistance and flexibility.
Moreover, an epoxy resin, a melamine resin, a phenol resin, a silicone resin, a urethane resin, etc. are used for a thermosetting resin. Especially, an epoxy resin, a silicone resin, and a urethane resin are suitable from heat resistance and a softness | flexibility.
Dispersants, lubricants, and plasticizers may be added to these resins. In particular, by using fatty acid esters as the dispersant, the filling rate of ceramics and carbon fiber materials can be increased and the characteristics can be improved. it can.
セラミックス粉末にはアルミナ、窒化アルミ、炭化珪素、窒化珪素、窒化硼素粉末が用いられる。粒子径は0.1μm以上100μm以下のものが好ましい、粒子径が0.1μmよりも小さくなると比表面積が増えるため樹脂中に添加できる量が少なくなり、100μmよりも大きくなると粉末間の隙間が大きくなり、自己放熱性が低下する。特に特性の面からは好ましい粒子径は0.3μm以上50μm以下、より好ましくは0.5μm以上40μm以下、さらに好ましくは1μm以上20μm以下である。
粒子形状は球状が好適である。セラミックス材料としては特にコスト面からアルミナセラミックスが好適であり、自己放熱性、熱伝導率の面からは窒化アルミが好適である。
本発明の材料に含まれるセラミックス粉末は1種類であっても、複数種であってもよく、材料中に占めるセラミックス粉末の割合は、総量で5体積%以上60体積%以下が好ましく、10体積%以上50体積%以下がより好ましく、20体積%以上45体積%以下が特に好ましい。
As the ceramic powder, alumina, aluminum nitride, silicon carbide, silicon nitride, or boron nitride powder is used. The particle size is preferably 0.1 μm or more and 100 μm or less. When the particle size is smaller than 0.1 μm, the specific surface area increases, so the amount that can be added to the resin is reduced. When the particle size is larger than 100 μm, the gap between the powders is increased. Thus, the self-heat dissipation performance is reduced. In particular, from the viewpoint of characteristics, a preferable particle diameter is 0.3 μm or more and 50 μm or less, more preferably 0.5 μm or more and 40 μm or less, and further preferably 1 μm or more and 20 μm or less.
The particle shape is preferably spherical. As the ceramic material, alumina ceramic is particularly preferable from the viewpoint of cost, and aluminum nitride is preferable from the viewpoint of self-heat dissipation and thermal conductivity.
The ceramic powder contained in the material of the present invention may be of one kind or plural kinds, and the ratio of the ceramic powder in the material is preferably 5% by volume or more and 60% by volume or less, and preferably 10% by volume. % To 50% by volume is more preferable, and 20% to 45% by volume is particularly preferable.
炭素繊維にはピッチ系炭素繊維、ピッチ系超高弾性率炭素繊維、カーボンナノチューブが用いられる。特に熱伝導性を向上させるためにはピッチ系超高弾性率炭素繊維は単体で500W/m・Kという銅、アルミ以上の熱伝導率を有しているため好ましい。また、カーボンナノチューブは少量で電磁波を吸収する性質を有している。しかしながらカーボンナノチューブは非常に高額であるため、コスト面を考慮するとピッチ系炭素繊維を主体としてピッチ系超高弾性率炭素繊維、カーボンナノチューブを添加する事が望ましい。
また、炭素繊維は総量で材料全量の1〜60体積%となるよう添加するのが好ましい。炭素繊維の添加量が1体積%よりも少ない場合には十分な熱伝導性と電磁波吸収能力が得られず、60体積%よりも多い場合には成形時の十分な流動性が得られない。特に、5体積%以上40体積%以下、さらに15体積%以上35体積%以下が好ましい。
本発明においてピッチ系超高弾性率炭素繊維とは、引っ張り弾性率が500GPa以上のものを指す。
Pitch-based carbon fibers, pitch-based ultrahigh modulus carbon fibers, and carbon nanotubes are used as the carbon fibers. In particular, in order to improve thermal conductivity, the pitch-based ultrahigh modulus carbon fiber is preferable because it has a thermal conductivity of 500 W / m · K or more of copper and aluminum. Carbon nanotubes have the property of absorbing electromagnetic waves in a small amount. However, since carbon nanotubes are very expensive, it is desirable to add pitch-based ultrahigh elastic modulus carbon fibers and carbon nanotubes, mainly pitch-based carbon fibers, in view of cost.
Moreover, it is preferable to add carbon fiber so that it may become 1-60 volume% of the total amount of material by the total amount. When the amount of carbon fiber added is less than 1% by volume, sufficient thermal conductivity and electromagnetic wave absorbing ability cannot be obtained, and when it is more than 60% by volume, sufficient fluidity during molding cannot be obtained. In particular, 5 volume% or more and 40 volume% or less are preferable, and 15 volume% or more and 35 volume% or less are preferable.
In the present invention, the pitch-based ultrahigh modulus carbon fiber refers to one having a tensile modulus of 500 GPa or more.
また、前記ピッチ系炭素繊維およびピッチ系超高弾性率炭素繊維の好ましい平均長さは1μm以上500μm以下であり、より好ましくは5μm以上500μm以下、特に好ましくは10μm以上100μm以下である。このましい平均直径は、1μm以上50μm以下、より好ましくは3μm以上20μm以下である。
また、カーボンナノチューブの好ましい平均長さは1μm以上50μm以下、このましい平均直径は、5nm以上100nm以下である。
Moreover, the preferable average length of the pitch-based carbon fiber and the pitch-based ultrahigh modulus carbon fiber is 1 μm or more and 500 μm or less, more preferably 5 μm or more and 500 μm or less, and particularly preferably 10 μm or more and 100 μm or less. The average diameter is preferably 1 μm or more and 50 μm or less, more preferably 3 μm or more and 20 μm or less.
The preferred average length of the carbon nanotubes is 1 μm or more and 50 μm or less, and the preferable average diameter is 5 nm or more and 100 nm or less.
本発明の材料中における、セラミックス粉末と炭素繊維の好ましい体積比率は95:5〜20:80、より好ましい比率は80:20〜25:75、特に好ましい比率は70:30〜30:70である。
また、材料中に占める炭素繊維とセラミックス粉末の合計割合は、好ましくは40体積%以上80体積%以下、より好ましくは50体積%以上70体積%以下、特に好ましくは60体積%以上70体積%以下である。
In the material of the present invention, the preferred volume ratio of the ceramic powder and the carbon fiber is 95: 5 to 20:80, the more preferred ratio is 80:20 to 25:75, and the particularly preferred ratio is 70:30 to 30:70. .
The total proportion of carbon fiber and ceramic powder in the material is preferably 40% by volume to 80% by volume, more preferably 50% by volume to 70% by volume, and particularly preferably 60% by volume to 70% by volume. It is.
熱可塑性樹脂とセラミックス及び炭素繊維との混合分散には加熱混練機、多軸押出機及び加熱ロール等を用いて行う。また、熱硬化性樹脂を母材に用いた場合にはミキサー、真空混合機、多軸押出機等を用いて行う。
得られた材料は射出成形、シート成形、押出成形若しくはプレス成形により所望する形状の成型品を作成することができる。得られた成型品は炭素繊維を含有するため強度が強く、また、セラミックス粉末を多く含むため、成形時に炭素繊維が一方向に配向することを防ぎ、材料の均等な強度向上と均質な熱伝導性及び電磁波吸収を実現することが可能となる。
成形方法では特に射出成形法を用いることにより、銅、アルミを原料としたヒートシンクと比較して、三次元複雑形状のヒートシンクを寸法精度良く、低温で成型することが可能である。また、銅、アルミのヒートシンクをダイカスト法で成型する場合と比較して、バリが少ない、肉厚1mm以下の三次元形状のヒートシンクを容易に成型できる。
Mixing and dispersing of the thermoplastic resin, ceramics, and carbon fiber is performed using a heating kneader, a multi-screw extruder, a heating roll, or the like. Further, when a thermosetting resin is used as a base material, it is performed using a mixer, a vacuum mixer, a multi-screw extruder or the like.
The obtained material can produce a molded article having a desired shape by injection molding, sheet molding, extrusion molding or press molding. The resulting molded product contains carbon fiber, so it has high strength and contains a lot of ceramic powder, which prevents the carbon fiber from being oriented in one direction during molding, improving the strength of the material evenly and ensuring uniform heat conduction. And absorption of electromagnetic waves can be realized.
In the molding method, in particular, by using an injection molding method, it is possible to mold a heat sink having a complicated three-dimensional shape at a low temperature with high dimensional accuracy as compared to a heat sink made of copper or aluminum. In addition, a three-dimensional heat sink having a wall thickness of 1 mm or less can be easily molded as compared with a case where a copper or aluminum heat sink is molded by a die casting method.
アルミに匹敵する放熱性を持つ材料を得るためには、樹脂の量は材料全体の60体積%以下であることが好ましい。好ましい樹脂の量は材料全量の20〜60体積%であり、より好ましくは25〜50体積%、特に好ましくは30〜40体積%である。セラミックス粉末の粒子径が小さすぎると、樹脂の添加量を増やす必要が生じるため、セラミックス粉末の粒子径は0.1〜100μmが好ましい。
特に、粒子径1μm〜40μmの球形のアルミナ粉末を細密充填できるように計算して配合し、これに炭素繊維を添加する事で、樹脂量を40体積%以下にまで低減することが可能となり、金属性の放熱材料に匹敵する成形材料を得ることができる。また、炭素繊維がこの細密充填されたセラミックス粉末の中でランダムに存在することで、シート成形、射出成形、押し出し成形で生じる炭素繊維の配向を低減できることで、炭素繊維を用いたヒートシンクに生じる放熱効果の方向依存性を低減させ、また均質な電磁波吸収効果を得ることができる。
In order to obtain a material having heat dissipation comparable to aluminum, the amount of resin is preferably 60% by volume or less of the entire material. A preferable amount of the resin is 20 to 60% by volume of the total amount of the material, more preferably 25 to 50% by volume, and particularly preferably 30 to 40% by volume. If the particle size of the ceramic powder is too small, it is necessary to increase the amount of resin added, and therefore the particle size of the ceramic powder is preferably 0.1 to 100 μm.
In particular, a spherical alumina powder having a particle diameter of 1 μm to 40 μm is calculated and blended so as to be finely packed, and by adding carbon fiber to this, it becomes possible to reduce the amount of resin to 40% by volume or less, A molding material comparable to a metallic heat dissipation material can be obtained. In addition, the presence of carbon fibers randomly in the finely packed ceramic powder can reduce the orientation of the carbon fibers generated by sheet molding, injection molding, and extrusion molding, and heat dissipation generated in the heat sink using carbon fibers. The direction dependency of the effect can be reduced, and a uniform electromagnetic wave absorption effect can be obtained.
以下、実施例に基づき、本発明の材料を詳細に説明する。 Hereinafter, based on an Example, the material of this invention is demonstrated in detail.
原料等の検討
放熱性と電磁波遮蔽性に優れた材料を得ることを目的として、様々な試作品を製造し特性を評価した。
Examination of raw materials, etc. Various prototypes were manufactured and properties were evaluated for the purpose of obtaining materials with excellent heat dissipation and electromagnetic wave shielding properties.
比較品1(焼結品)
放熱性の高いアルミナセラミックス若しくは、窒化アルミセラミックス粉末を、電磁波吸収性のあるカーボン材料とともに、有機バインダと混練して成形材料を作製し、この成形材料を用いて射出成形によりヒートシンク形状の成形体を得て、脱脂、焼結を行って、焼結体からなるヒートシンクを作製した。
しかし、焼結密度が向上せず、焼結体内部に気孔が10%程度存在する事から、期待した放熱効果が得られなかった。これはセラミックスとカーボン材料の濡れ性が無く、焼結時にカーボン材料がセラミックスの焼結を妨げる為であることが確認され、以後の実験は断念した。
Comparative product 1 (sintered product)
A heat-dissipating alumina ceramic or aluminum nitride ceramic powder is mixed with an organic binder together with an electromagnetic wave-absorbing carbon material to produce a molding material. Using this molding material, a heat sink-shaped molded body is formed by injection molding. Obtained, degreased and sintered to produce a heat sink made of a sintered body.
However, since the sintered density was not improved and the pores existed in the sintered body at about 10%, the expected heat dissipation effect could not be obtained. It was confirmed that this was because there was no wettability between the ceramics and the carbon material and the carbon material prevented the ceramics from sintering during sintering, and the subsequent experiments were abandoned.
比較品2(焼結品)
放熱性の高いアルミナセラミックス若しくは、窒化アルミセラミックス粉末を、電磁波シールド性のある銅粉末とともに、有機バインダと混練して成形材料を作製し、この成形材料を用いて射出成形によりヒートシンク形状の成形体を得て、脱脂、焼結を行って、焼結体からなるヒートシンクを作製した。
しかし、焼結時に焼結密度が向上せず、焼結体内部に気孔が10%程度存在する事から、期待した放熱効果が得られなかった。これはセラミックスと銅粉末の濡れ性が無いことと、銅の融点がセラミックスの焼結温度よりも500℃低いことで、焼結時に銅が溶融しセラミックスの焼結を妨げる為であることが確認され、以後の実験は断念した。
Comparative product 2 (sintered product)
A heat-dissipating alumina ceramic or aluminum nitride ceramic powder is mixed with an organic binder together with an electromagnetic shielding copper powder to produce a molding material. Using this molding material, a heat sink-shaped molded body is formed by injection molding. Obtained, degreased and sintered to produce a heat sink made of a sintered body.
However, since the sintered density was not improved during sintering and the pores existed in the sintered body at about 10%, the expected heat dissipation effect could not be obtained. This is because there is no wettability between ceramics and copper powder, and because the melting point of copper is 500 ° C lower than the sintering temperature of ceramics, the copper melts during sintering and prevents ceramics from sintering. The subsequent experiment was abandoned.
比較品3(樹脂材料)
樹脂に、放熱性の高いセラミックス粉末と電磁波シールド性に優れたフェライト粉末とを混練して成形材料とし、これを用いてシート成形および射出成形を行った。
放熱性を測定したところ、フェライト粉末の熱伝導が低いため、熱が内部に蓄積し金属の放熱材料に匹敵する放熱性が得られなかった。
Comparative product 3 (resin material)
The resin was kneaded with ceramic powder with high heat dissipation and ferrite powder with excellent electromagnetic shielding properties to form a molding material, which was used for sheet molding and injection molding.
When the heat dissipation was measured, the heat conduction of the ferrite powder was low, so heat was accumulated inside, and a heat dissipation comparable to a metal heat dissipation material could not be obtained.
比較品4(樹脂材料)
樹脂に、放熱性の高いセラミックス粉末と電磁波シールド性のある銅粉末を混合した材料の作製を試みた。熱伝導性と電磁波遮蔽性を上げるため、20μm以下の銅粉末を用いて加熱混練を行ったが、混練時に銅粉末が急激に酸化するため、期待した電磁波遮蔽特性及び放熱性を得ることができなかった。
Comparative product 4 (resin material)
An attempt was made to produce a material in which ceramic powder with high heat dissipation and copper powder with electromagnetic shielding properties were mixed with resin. In order to increase thermal conductivity and electromagnetic wave shielding, heat kneading was performed using copper powder of 20 μm or less, but the copper powder rapidly oxidized during kneading, so that the expected electromagnetic wave shielding characteristics and heat dissipation can be obtained. There wasn't.
比較品5(樹脂材料)
セラミックス粉末およびカーボン材料を用いて樹脂と混練して、安定した性質と優れた熱伝導性の材料を得ることを試みた。
カーボン材料として黒鉛粉末を用いたところ、粒子径が非常に小さく表面積が大きいため、樹脂の添加量を40体積%以下にして成形材料を作製することが困難であり、期待する放熱性と電磁波遮蔽特性を得ることができなかった。
Comparative product 5 (resin material)
An attempt was made to obtain a material with stable properties and excellent thermal conductivity by kneading with a resin using ceramic powder and a carbon material.
When graphite powder is used as the carbon material, the particle size is very small and the surface area is large. Therefore, it is difficult to produce a molding material with a resin addition amount of 40% by volume or less. The characteristics could not be obtained.
本発明品
セラミックス粉末およびカーボン材料を用いて樹脂と混練して、安定した性質と優れた熱伝導性の材料を得ることを試みた。
カーボン材料として炭素繊維を用いたところ、PAN系炭素繊維とピッチ系炭素繊維のうち、ピッチ系炭素繊維を用いる事で、放熱性を上げることが可能となった。
さらに、カーボンナノチューブを用いたところ、添加量2〜5%と少量においても電磁波遮蔽特性に優れることが明らかとなった。
また、セラミックス粉末として、特にアルミナ粉末、窒化アルミ粉末、炭化珪素粉末、窒化珪素粉末、窒化硼素粉末を用いることにより、放熱性を向上させることに成功した。
また、アルミに匹敵する放熱性に優れた材料を得るためには、樹脂の量が材料全体の60体積%以下が好ましいことが分かった。特に樹脂量を40体積%以下にまで低減することで、金属性の放熱材料に匹敵する成形材料を得ることができた。
このため、最初はセラミックス粉末同士の距離を近づけるために、粒子径0.1μm未満のセラミックス粉末を用いていたが、粉末粒子径が小さいほど樹脂の添加量を多くする必要があるため、粒子径0.1μm〜100μmの粉末を用いることが適当であることが分かった。
An attempt was made to obtain a material having stable properties and excellent thermal conductivity by kneading with a resin using the ceramic powder of the present invention and a carbon material.
When carbon fiber was used as the carbon material, it was possible to improve heat dissipation by using pitch-based carbon fiber among PAN-based carbon fiber and pitch-based carbon fiber.
Furthermore, when carbon nanotubes were used, it became clear that the electromagnetic wave shielding properties were excellent even in a small amount of 2 to 5%.
In addition, the use of alumina powder, aluminum nitride powder, silicon carbide powder, silicon nitride powder, and boron nitride powder as the ceramic powder has succeeded in improving heat dissipation.
Moreover, in order to obtain the material excellent in the heat dissipation comparable with aluminum, it turned out that the quantity of resin is 60 volume% or less of the whole material. In particular, by reducing the resin amount to 40% by volume or less, it was possible to obtain a molding material comparable to a metallic heat dissipation material.
For this reason, in order to reduce the distance between the ceramic powders at first, ceramic powders having a particle diameter of less than 0.1 μm were used. However, the smaller the powder particle diameter, the greater the amount of resin added. It has been found suitable to use a powder of 0.1 μm to 100 μm.
特性の評価
本発明の材料からなるシートおよび比較のためのシート(セラミックス粉末/炭素繊維の一方のみを含む)を作製し、その特性を検討した。
実施例及び比較例に用いた材料の配合表を表1に示す。
Evaluation of Characteristics A sheet made of the material of the present invention and a comparative sheet (including only one of ceramic powder / carbon fiber) were prepared, and the characteristics were examined.
Table 1 shows a blending table of materials used in Examples and Comparative Examples.
シートの作製
熱可塑性樹脂を用いる場合、樹脂をあらかじめ0.5Lの加熱混練機でポリプロピレンの場合には200度に設定し、ナイロン樹脂の場合には250度に設定して10分間混合し十分溶融させた後にセラミックス粉末及び炭素繊維を徐々に添加して1時間加熱混練を行い、取り出した塊をシート状にした後、粉砕機にかけて成形材料とした。
得られた成形材料を型締め力20トンの射出成形機を用いて、温度測定に関しては35mm×35mm×厚み2mmの成形体を作成してこれを用いた。電磁波吸収の測定には100mm×100mm×厚み1.5mmの成形体を成形してこれを用いた。
熱硬化性樹脂であるシリコーン樹脂の場合は、2成分付加型液状シリコーンゴムを用い、主剤100重量部に対して硬化剤10重量部を混合させたものとした。これにセラミックス粉末及び炭素繊維を添加した後、1Lの真空脱泡混合機を用いて、25℃で真空脱泡しながら撹拌混合を30分間行い、取り出した後、ポリエチレンテレフタレート(PET)フィルムに2mm(温度測定用)と1.5mm(電磁波測定用)の厚みにコーティングした後、25℃で24時間後にPETフィルムから離型し、25℃で48時間放置した後、測定を行った。シートのサイズは上述通りとした。
Preparation of sheet When using thermoplastic resin, set the resin in advance in a 0.5 L heating kneader to 200 degrees in the case of polypropylene and 250 degrees in the case of nylon resin, mix for 10 minutes and melt sufficiently Then, the ceramic powder and carbon fiber were gradually added and heat-kneaded for 1 hour. The lump taken out was formed into a sheet shape, and then subjected to a pulverizer to obtain a molding material.
Using the obtained molding material, an injection molding machine with a clamping force of 20 tons was used to prepare a molded body of 35 mm × 35 mm × thickness 2 mm for temperature measurement. For measurement of electromagnetic wave absorption, a molded body of 100 mm × 100 mm × thickness 1.5 mm was molded and used.
In the case of a silicone resin which is a thermosetting resin, a two-component addition type liquid silicone rubber was used, and 10 parts by weight of a curing agent was mixed with 100 parts by weight of the main agent. After adding ceramic powder and carbon fiber to this, stirring and mixing were performed for 30 minutes while vacuum defoaming at 25 ° C. using a 1 L vacuum defoaming mixer, and after taking out, 2 mm was added to the polyethylene terephthalate (PET) film. After coating to a thickness of 1.5 mm (for measuring electromagnetic waves) and 1.5 mm (for measuring electromagnetic waves), the film was released from the PET film after 24 hours at 25 ° C. and allowed to stand for 48 hours at 25 ° C., and measurements were taken. The sheet size was as described above.
なお、実施例及び比較例に用いたアルミナ粉末は平均粒子径10μmとした。また、実施例及び比較例で用いたピッチ系炭素繊維及びピッチ系超高弾性炭素繊維は平均直径10μm、平均長さ50μmとした。
電磁波の測定に関してはアドバンテスト製、スペクトラムアナライザR3132を用いて0.1MHz〜1GHzの電磁波遮蔽特性を測定した。
また、放熱特性の測定については下記に示す方法により測定を行った。幅15mm、厚み2mm、長さ100mmの銅板を、熱源を使用して80℃まで温度を上げて、30分均熱を確認した後、試料(35mm角、2mm厚)を前記銅板の上に置いて、試料から5mm後方の銅板の30分後の温度を測定した。
The alumina powder used in the examples and comparative examples had an average particle size of 10 μm. The pitch-based carbon fibers and pitch-based ultrahigh elasticity carbon fibers used in Examples and Comparative Examples had an average diameter of 10 μm and an average length of 50 μm.
Regarding the measurement of electromagnetic waves, the electromagnetic wave shielding characteristics of 0.1 MHz to 1 GHz were measured using a spectrum analyzer R3132 manufactured by Advantest.
Moreover, about the measurement of the thermal radiation characteristic, it measured by the method shown below. A copper plate having a width of 15 mm, a thickness of 2 mm, and a length of 100 mm was heated to 80 ° C. using a heat source, and after confirming soaking for 30 minutes, a sample (35 mm square, 2 mm thickness) was placed on the copper plate. The temperature after 30 minutes of the copper plate 5 mm behind the sample was measured.
結果を表1に示す。
測定結果から、本発明の材料からなるシートは何れも30分後の銅板の温度が72℃以下と放熱性に優れ、且つ1MHz〜1GHzの間に於いて電磁波遮蔽特性が−10dB以上と広帯域で優れた電磁波遮蔽性を示すことが確認された。なお、銅板を同条件で測定した場合には放熱温度は71℃、アルミニウムでは73℃となり、本発明にかかる材料が、アルミ、銅と同程度以上の放熱特性(吸熱効果)を有することが分かった。さらに、電磁波遮蔽特性においては低周波領域(100MHz以下)において−30dBを越える優れた値を示し、また1GHzまで安定したシールド特性を示す優れた材料であることが確認された。 From the measurement results, the sheet made of the material of the present invention is excellent in heat dissipation, with the temperature of the copper plate after 30 minutes being 72 ° C. or less, and the electromagnetic wave shielding property is −10 dB or more in a wide band between 1 MHz and 1 GHz. It was confirmed that excellent electromagnetic shielding properties were exhibited. When the copper plate was measured under the same conditions, the heat release temperature was 71 ° C. and that for aluminum was 73 ° C., indicating that the material according to the present invention has a heat release characteristic (endothermic effect) equal to or higher than that of aluminum and copper. It was. Furthermore, in the electromagnetic wave shielding characteristics, it was confirmed that the material exhibits an excellent value exceeding −30 dB in a low frequency region (100 MHz or less), and is an excellent material exhibiting a stable shielding characteristic up to 1 GHz.
なお、銅板は赤外線をほとんど発しないため、赤外線サーモグラフィーでデータを取ると、実温度に比べて測定温度がはるかに低くなるが、本発明にかかる材料では、サーモグラフィーの測定温度と実温度がほぼ一致するため、熱放射率がほぼ1に近いことが確認された。このため、本発明にかかる材料の放熱特性(相手の熱を下げる効果[吸熱効果])は、熱放射による自己放熱性(自分の熱を発散させる効果)の高さに起因すると考えられる。
また、本発明にかかる炭素繊維は、電磁波吸収特性に優れるため、本発明にかかる材料は、電磁波遮蔽性だけでなく、電磁波吸収性にも優れていると考えられる。電磁波を試料に入射させた場合、入射量=反射量+吸収量+透過量の関係が成り立つが、電磁波遮蔽性が高いとは、透過量が小さいことを意味し、電磁波吸収性が高いとは透過量と反射量が小さいことを意味する。電磁波吸収性の高い材料は、反射干渉による弊害を防ぐことができる。
Note that the copper plate emits almost no infrared rays, so when taking data with infrared thermography, the measured temperature is much lower than the actual temperature, but with the material according to the present invention, the measured temperature of the thermography is almost the same as the actual temperature. Therefore, it was confirmed that the thermal emissivity was close to 1. For this reason, it is considered that the heat dissipation characteristics of the material according to the present invention (the effect of reducing the heat of the other party [endothermic effect]) are caused by the high self-heat dissipation property (effect of dissipating its own heat) due to thermal radiation.
Moreover, since the carbon fiber concerning this invention is excellent in an electromagnetic wave absorption characteristic, it is thought that the material concerning this invention is excellent not only in electromagnetic wave shielding but also in electromagnetic wave absorptivity. When an electromagnetic wave is incident on the sample, the relationship of incident amount = reflection amount + absorption amount + transmission amount holds, but high electromagnetic wave shielding means that the transmission amount is small, and that electromagnetic wave absorption is high. It means that the amount of transmission and reflection is small. A material having high electromagnetic wave absorptivity can prevent harmful effects caused by reflection interference.
本発明にかかる材料は、優れた放熱性と電磁波遮蔽性の両方を併せ持つため、従来2つの部品が用いられていたものを一体化することができ、製品の薄型化を図ることができる。また、本発明にかかる材料は広帯域での電磁波遮蔽性を有するため、電磁波遮蔽のみを目的として使用するにも好適である。例えば、近年の通信技術の発達により、携帯電話、パソコン、ゲーム機等から発生する電磁波が人体に悪影響を及ぼす可能性が指摘されているが、本発明はこのような電磁波からの保護を目的として使用することもできる。 Since the material according to the present invention has both excellent heat dissipation and electromagnetic wave shielding properties, it has been possible to integrate two components that have been used in the past, and to reduce the thickness of the product. In addition, since the material according to the present invention has an electromagnetic wave shielding property in a wide band, it is suitable for use only for electromagnetic wave shielding. For example, with the recent development of communication technology, it has been pointed out that electromagnetic waves generated from mobile phones, personal computers, game machines, etc. may adversely affect the human body, but the present invention aims to protect against such electromagnetic waves. It can also be used.
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CN114541136A (en) * | 2022-01-27 | 2022-05-27 | 江苏亨睿航空工业有限公司 | Modified silicon carbide sizing agent for improving wave absorption performance of carbon fiber and preparation method thereof |
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