JP3868141B2 - Method for producing spherical silica powder - Google Patents
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- JP3868141B2 JP3868141B2 JP06506699A JP6506699A JP3868141B2 JP 3868141 B2 JP3868141 B2 JP 3868141B2 JP 06506699 A JP06506699 A JP 06506699A JP 6506699 A JP6506699 A JP 6506699A JP 3868141 B2 JP3868141 B2 JP 3868141B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、半導体樹脂封止用充填材に好適な球状シリカ粉末の製造方法に関する。
【０００２】
【従来の技術】
純度の高いシリカを高温で溶融し冷却したものは、非晶質網目構造を持ち、低膨脹性、耐熱衝撃性、低熱伝導性であるので耐熱材料として用いられている。また、その粉末も化学的に安定で高い絶縁性を持ち、高周波誘電体損失も少ないことから、半導体封止樹脂用フィラーとして用いられ、特に球状のものは流動性や充填性の向上に役立っている。中でも、真球に近いものほど充填性、流動性、耐金型摩耗性に優れているので、球形度の高いフィラーが追求されてきている。
【０００３】
一般に、シリカ等の破砕品原料を溶融球状化する場合、原料中の微粉粒子は単独では球状化しにくく、微粉粒子同士あるいは微粉粒子と粗粉粒子が合着結合して、原料よりも粗い粒子になることが多い。また、粗粉粒子は微粉粒子に比べて溶融しにくいため、より長い火炎滞留時間が必要となる。
【０００４】
そのため、粒度の粗い高球形度フィラーを製造する場合、粗めに粉砕した原料を単に用いると、微粉粒子と粗粉粒子の合着により、得られた粒子の球形度が低下してしまう。更には、シリカ原料粉末を混入させたキャリアガスの流速によっては、粗粉粒子の溶融球状化が不十分となる。
【０００５】
この問題を解消するため、特開平６−５６４４５公報では、溶融原料噴出口における溶融原料のキャリアガス流速を３〜６０ｍ／ｓ、燃焼火炎ガス流速を３０〜２００ｍ／ｓとすることが提案されているが、合着による球形度の低下については何の配慮もなされていない。特に、４５μｍ以上の粗い粒子を含むシリカ粉末原料の球状化を行う際、合着による球形度の低下改善については何も記載されていない。
【０００６】
【発明が解決しようとする課題】
本発明は、上記に鑑みてなされたものであり、その目的は、平均粒径の大きな球状溶融シリカ粉末をその球形度を高めて容易に製造することである。
【０００７】
【課題を達成するための手段】
本発明の課題は、火炎に噴射されるシリカ粉末原料の粒度分布と噴射速度を適正化し、溶融状態を最適化することによって達成することができる。
【０００８】
すなわち、本発明は、火炎中にシリカ粉末原料を噴射して球状シリカ粉末を製造する方法において、上記シリカ粉末原料が、平均粒径ｄ５０＝２０〜８０μｍ、累積１０％粒子径ｄ１０＝１０μｍ以上、ｄ９０／ｄ１０≦５（但し、ｄ９０は累積９０％粒子径である。）の粒度分布を有し、それをキャリアガスに混入させ、そのガス流速を１５〜４０ｍ／ｓにして、同心円に形成された内炎と外炎との間に噴射することを特徴とする球状シリカ粉末の製造方法である。本発明の製造方法は、粒径４５〜８０μｍにおける粉末の球形度が０．９以上である球状シリカ粉末を得るのに特に好適なものである。
【０００９】
【発明の実施の形態】
以下、更に詳しく本発明について説明する。
【００１０】
本発明で使用される原料のシリカ粉末は、比較的良質のＳｉＯ2を主成分とする珪石、水晶、珪砂等を振動ミル等の手段で粉砕し、好ましくは２回以上の分級を行って得られたものである。
【００１１】
本発明においては、そのシリカ粉末原料の粒度分布に大きな特徴があり、平均粒径ｄ５０が２０〜８０μｍで、累積１０％粒子径ｄ１０が１０μｍ以上、好ましくは２０μｍ以上であり、しかもｄ９０／ｄ１０≦５を満たすことが重要なことである。
【００１２】
シリカ粉末原料の平均粒径ｄ５０が２０μｍ未満では、原料噴射時の分散が悪くなり球形度が低下し、８０μｍをこえると、粒子の球状化が不十分となる。一方、累積１０％粒子径ｄ１０が１０μｍ未満では、微粉粒子の割合が多くなり、それと粗粉粒子とが合着する割合が多くなって、球形度の低下を招き、またｄ９０／ｄ１０が５をこえると、球状化できる粒子の割合が少なくなり、粒径４５〜８０μｍの高球形度の溶融シリカ粉末の収得率が低下する。これらの結果、いずれの場合も、平均粒径の大きな、高球形度の球状溶融シリカ粉末を容易に製造することができなくなる。本発明においては、シリカ粉末原料の粒度調整ないしは得られた球状溶融シリカ粉末の分級によって生成した８０μｍをこえる粒子は、原料工程に戻して再使用されることが望ましい。
【００１３】
本発明のようなシリカ粉末原料の粒度分布は、従来の代表的な一例が、平均粒径ｄ５０が１７μｍ、累積１０％粒子径ｄ１０が１．８μｍ、ｄ９０／ｄ１０が３４程度であったことと比べて特異的である。
【００１４】
シリカ粉末原料は、酸素ガス等のをキャリアガスに混入して火炎中に噴射され、溶融球状化処理されて高球形度の粉末となる。火炎の形成は、可燃性ガスと、酸素、空気等の助燃ガスによって行われ、可燃ガスとしては、アセチレン、エチレン、プロパン、ブタン等が使用される。
【００１５】
本発明においては、シリカ粉末原料をキャリアガスに混入させて噴射する際、そのキャリアガス流速を１５〜４０ｍ／ｓ、好ましくは２０〜３０ｍ／ｓとすることが重要なことである。この条件は、従来の代表的な一例が、４８ｍ／ｓ程度であったことと比べて著しく異なっている。キャリアガス流速が１５ｍ／ｓ未満では、原料噴射に支障を来しバーナーで原料詰まりが多くなり、また、４０ｍ／ｓをこえると、火炎滞留時間が短くなり、溶融球状化が不十分となる。
【００１６】
シリカ粉末原料の噴射方法は、同心円状に形成される火炎の中心に噴射させるよりは、同心円上に形成される内炎と外炎において、両火炎の間に噴射させることが好ましい。これによって、シリカ粒子が火炎と接触し易くなり、粒径の大きなシリカ粉末原料であっても球形度が高くなり、溶融率も向上する。
【００１７】
本発明の製造方法は、粒径４５〜８０μｍにおける球形度が０．９以上の球状シリカ粉末を得るのに特に好適であり、このような球状シリカ粉末は、半導体チップ封止用樹脂組成物のフィラーとしての用途があり、樹脂の高流動性と高強度を従来以上に高めることが可能となる。
【００１８】
本発明でいう球形度は、走査型電子顕微鏡（例えば、日本電子社製「ＪＳＭ−Ｔ２００型」）と画像解析装置（例えば、日本アビオニクス社製）を用い、次のようにして測定することができる。
【００１９】
すなわち、試料のＳＥＭ写真から粒子の投影面積（Ａ）と周囲長（ＰＭ）を測定する。周囲長（ＰＭ）に対応する真円の面積を（Ｂ）とすると、その粒子の球形度はＡ／Ｂとして表示できる。そこで、試料粒子の周囲長（ＰＭ）と同一の周囲長を持つ真円を想定すると、ＰＭ＝２πｒ、Ｂ＝πｒ2であるから、Ｂ＝π×（ＰＭ／２π）2 となり、個々の粒子の球形度は、球形度＝Ａ／Ｂ＝Ａ×４π／（ＰＭ）2として算出することができる。そこで、球状シリカ粒子の集合体である球状シリカ粉末の球形度は、球状シリカ粉末から任意に選んだ１０００個の粒子について測定し、その平均値で代表させるものとする。
【００２０】
また、溶融球状化の指標である溶融率は、粉末Ｘ線回折装置（例えば、ＲＩＧＡＫＵ社製「Ｍｉｎｉ Ｆｌｅｘ」）を用い、ＣｕＫα線の２θが２６°〜２７．５°の範囲において試料のＸ線回折分析を行い、特定回折ピークの強度比から測定することができる。すなわち、結晶シリカは、２６．７°に主ピークが存在するが、溶融シリカではこの位置には存在しない。溶融シリカと結晶シリカが混在していると、それらの割合に応じた２６．７°のピーク高さが得られるので、結晶シリカ標準試料のＸ線強度に対する試料のＸ線強度の比から、結晶シリカ混在率（試料のＸ線強度／結晶シリカのＸ線強度）を算出し、式、溶融率（％）＝（１−結晶シリカ混在率）×１００、から溶融率を求めることができる。
【００２１】
また、本発明における粒度分布は、試料０．３ｇを水に分散し、レーザー回折式粒度分布測定装置（シーラスグラニュロメーター「モデル７１５」）によって測定された値である。
【００２２】
【実施例】
以下、実施例、比較例をあげて更に具体的に本発明を説明する。
【００２３】
実施例で用いた装置は、内炎と外炎の形成と、両火炎の間にシリカ粉末原料の噴射とを行うことができるバーナーの設置された竪型溶融炉と、得られた球状シリカ粉末の捕集系とから構成されている。火炎が形成されている領域が溶融ゾーンであり、それに続いて溶融粒子の冷却固化の行われる冷却ゾーンがあり、溶融ゾーンの終わり付近から冷却用空気が供給できるようになっている。捕集系には、重力沈降室、サイクロン、バグフィルター等の捕集機が設置され、それらの捕集機の性能に応じた粒子が段階的に取得される。
【００２４】
実施例１〜５、比較例１〜６
珪石を振動ミルにより平均粒径２０μｍ程度に微粉砕した。このシリカ粉末を、二台直列のラインで構成された空気分級機で粗粉と微粉を除去し、種々の粒度分布を有するシリカ粉末原料を調整した。このシリカ粉末原料を、酸素をキャリアガスとし、その流速を表１に示される条件として、内炎と外炎の間（実施例１〜５、比較例１〜５）又は火炎の中心（比較例６）に噴射して球状化処理を行った。重力沈降室より捕集された球状シリカ粉末を篩分けし、８０μｍ下粒子の取得率と溶融率、及び粒径４５〜８０μｍ粒子の球形度を測定した。それらの結果を表１に示す。
【００２５】
【表１】
表１から、以下のことがわかる。
【００２７】
キャリアガス流速については、それが１５〜４０ｍ／ｓである場合において、球形度０．９以上、溶融率９７％以上で、しかも８０μｍ下粒子の収得率が向上した（実施例１〜５）。これに対し、キャリアガス流速が４０ｍ／ｓをこえると、火炎滞留時間が短いため、溶融率は低下し（比較例２）、また１５ｍ／ｓ未満であると、原料噴射に支障を来しバーナーで原料詰まりが頻繁に起り、８０μｍ下粒子の収得率、球形度、溶融率がともに低下した（比較例１）。
【００２８】
シリカ粉末原料の粒度分布については、累積１０％粒子径ｄ１０が１０μｍ未満では、微粉粒子が多いため、粗粉粒子と合着し球形度が低下し、肥大化も進行した（比較例３）。また、ｄ９０／ｄ１０が５をこえる場合（比較例４）、平均粒径が８０μｍをこえる場合（比較例５）には、８０μｍ下粒子の収得率が大幅に低下した。
【００２９】
比較例６は、シリカ粉末原料を火炎の中心に噴射したこと以外は、実施例４に準じて行ったものであるが、内炎と外炎との間に噴射を行わなかった分だけ、実施例４よりも球形度と溶融率が低くなった。
【００３０】
【発明の効果】
本発明によれば、平均粒径の大きな球状シリカ粉末をその球形度を高めて容易に製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a spherical silica powder suitable for a semiconductor resin sealing filler.
[0002]
[Prior art]
High-purity silica melted at high temperature and cooled has an amorphous network structure, and is used as a heat-resistant material because it has low expansion, thermal shock resistance, and low thermal conductivity. Also, the powder is chemically stable and has high insulation, and since it has low high-frequency dielectric loss, it is used as a filler for semiconductor encapsulating resins, especially spherical ones that help improve fluidity and fillability. Yes. Among these, fillers with high sphericity have been pursued because the closer to the true sphere, the better the filling property, fluidity, and mold wear resistance.
[0003]
In general, when pulverized raw materials such as silica are melted and spheroidized, the fine particles in the raw material are not easily spheroidized alone, and the fine particles are fused together or the fine particles and the coarse particles are bonded together to form particles that are coarser than the raw materials. Often becomes. Moreover, since coarse powder particles are less likely to melt than fine powder particles, a longer flame residence time is required.
[0004]
Therefore, when producing a coarser high-sphericity filler, simply using a coarsely pulverized raw material results in a decrease in the sphericity of the obtained particles due to the coalescence of the fine and coarse particles. Further, depending on the flow rate of the carrier gas mixed with the silica raw material powder, the melt spheroidization of the coarse particles becomes insufficient.
[0005]
In order to solve this problem, JP-A-6-56445 proposes that the carrier gas flow rate of the molten raw material at the molten raw material outlet is 3 to 60 m / s and the combustion flame gas flow rate is 30 to 200 m / s. However, no consideration is given to the decrease in sphericity due to coalescence. In particular, when spheroidizing a silica powder raw material containing coarse particles of 45 μm or more, nothing is described about improvement in reduction of sphericity by coalescence.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and an object of the present invention is to easily produce a spherical fused silica powder having a large average particle diameter by increasing its sphericity.
[0007]
[Means for achieving the object]
The object of the present invention can be achieved by optimizing the particle size distribution and the injection speed of the silica powder raw material injected into the flame and optimizing the molten state.
[0008]
That is, the present invention is a method for producing a spherical silica powder by injecting a silica powder raw material into a flame, wherein the silica powder raw material has an average particle diameter d50 = 20 to 80 μm, a cumulative 10% particle diameter d10 = 10 μm or more, It has a particle size distribution of d90 / d10 ≦ 5 (where d90 is a cumulative 90% particle size) and is mixed with a carrier gas, and its gas flow rate is 15 to 40 m / s to form concentric circles. A method for producing spherical silica powder, characterized by spraying between an inner flame and an outer flame . The production method of the present invention is particularly suitable for obtaining a spherical silica powder having a particle size of 45 to 80 μm and having a sphericity of 0.9 or more.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
[0010]
The raw silica powder used in the present invention is obtained by pulverizing silica, crystal, silica sand, etc., which has a relatively high quality SiO 2 as a main component, by means of a vibration mill or the like, and preferably performing classification twice or more. It is what was done.
[0011]
In the present invention, the particle size distribution of the silica powder raw material is greatly characterized by an average particle size d50 of 20 to 80 μm, a cumulative 10% particle size d10 of 10 μm or more, preferably 20 μm or more, and d90 / d10 ≦ It is important to satisfy 5.
[0012]
When the average particle diameter d50 of the silica powder raw material is less than 20 μm, the dispersion during the raw material injection becomes poor and the sphericity is lowered, and when it exceeds 80 μm, the spheroidization of the particles becomes insufficient. On the other hand, if the cumulative 10% particle diameter d10 is less than 10 μm, the proportion of fine particles increases, the proportion of coalesced with coarse particles increases, resulting in a decrease in sphericity, and d90 / d10 is 5. When it exceeds, the ratio of the particles that can be spheroidized decreases, and the yield of high sphericity fused silica powder having a particle size of 45 to 80 μm decreases. As a result, in any case, it becomes impossible to easily produce a spherical fused silica powder having a large average particle diameter and a high sphericity. In the present invention, it is desirable that particles exceeding 80 μm produced by adjusting the particle size of the silica powder raw material or classifying the obtained spherical fused silica powder are returned to the raw material process and reused.
[0013]
As for the particle size distribution of the silica powder raw material as in the present invention, a typical representative example is that the average particle size d50 is 17 μm, the cumulative 10% particle size d10 is 1.8 μm, and d90 / d10 is about 34. It is specific.
[0014]
The silica powder raw material is mixed with a carrier gas such as oxygen gas and injected into the flame, and is subjected to a melt spheronization treatment to obtain a high sphericity powder. The flame is formed by a combustible gas and an auxiliary combustion gas such as oxygen or air. As the combustible gas, acetylene, ethylene, propane, butane, or the like is used.
[0015]
In the present invention, when the silica powder raw material is mixed with the carrier gas and injected, it is important that the carrier gas flow rate is 15 to 40 m / s, preferably 20 to 30 m / s. This condition is significantly different from that of a typical representative example of about 48 m / s. If the carrier gas flow rate is less than 15 m / s, the injection of the material is hindered and the material clogging is increased by the burner. If the carrier gas flow rate exceeds 40 m / s, the flame residence time is shortened and the melt spheroidization becomes insufficient.
[0016]
In the method of injecting the silica powder raw material, it is preferable to inject between the two flames in the inner flame and the outer flame formed on the concentric circles, rather than injecting into the center of the flame formed concentrically. As a result, the silica particles can easily come into contact with the flame, and even if the silica powder raw material has a large particle size, the sphericity is increased and the melting rate is improved.
[0017]
The production method of the present invention is particularly suitable for obtaining a spherical silica powder having a particle size of 45 to 80 μm and a sphericity of 0.9 or more. Such a spherical silica powder is a resin composition for sealing a semiconductor chip. There is a use as a filler, and it becomes possible to increase the high fluidity and strength of the resin more than before.
[0018]
The sphericity referred to in the present invention can be measured as follows using a scanning electron microscope (for example, “JSM-T200 type” manufactured by JEOL Ltd.) and an image analyzer (for example, manufactured by Nippon Avionics Co., Ltd.). it can.
[0019]
That is, the projected area (A) and the perimeter (PM) of the particle are measured from the SEM photograph of the sample. When the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle can be displayed as A / B. Therefore, assuming a perfect circle having the same peripheral length as the sample particle (PM), PM = 2πr and B = πr 2 , so that B = π × (PM / 2π) 2 , and each particle The sphericity can be calculated as sphericity = A / B = A × 4π / (PM) 2 . Therefore, the sphericity of the spherical silica powder, which is an aggregate of spherical silica particles, is measured for 1000 particles arbitrarily selected from the spherical silica powder, and is represented by the average value.
[0020]
In addition, the melting rate, which is an index of melt spheroidization, is measured using a powder X-ray diffractometer (for example, “Mini Flex” manufactured by RIGAKU), and the 2θ of CuKα ray is in the range of 26 ° to 27.5 °. It can be measured from the intensity ratio of specific diffraction peaks by performing line diffraction analysis. That is, crystalline silica has a main peak at 26.7 °, but fused silica does not exist at this position. When fused silica and crystalline silica are mixed, a peak height of 26.7 ° corresponding to the ratio can be obtained. From the ratio of the X-ray intensity of the sample to the X-ray intensity of the crystalline silica standard sample, the crystal The silica mixing ratio (X-ray intensity of sample / X-ray intensity of crystalline silica) is calculated, and the melting ratio can be obtained from the formula, melting rate (%) = (1-crystalline silica mixing rate) × 100.
[0021]
Further, the particle size distribution in the present invention is a value measured by using a laser diffraction particle size distribution measuring device (Cirrus Granurometer “Model 715”) in which 0.3 g of a sample is dispersed in water.
[0022]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
[0023]
The apparatus used in the examples includes a vertical melting furnace equipped with a burner capable of forming an inner flame and an outer flame, and injecting a silica powder raw material between both flames, and the obtained spherical silica powder And the collection system. A region where a flame is formed is a melting zone, followed by a cooling zone where cooling and solidification of molten particles is performed, and cooling air can be supplied from the vicinity of the end of the melting zone. In the collection system, a collection device such as a gravity sedimentation chamber, a cyclone, a bag filter or the like is installed, and particles corresponding to the performance of the collection device are acquired in stages.
[0024]
Examples 1-5 , Comparative Examples 1-6
Silica stone was finely pulverized to an average particle size of about 20 μm by a vibration mill. From this silica powder, coarse powder and fine powder were removed by an air classifier constituted by a series line of two units to prepare silica powder raw materials having various particle size distributions. Using this silica powder raw material as a carrier gas and the flow rate as shown in Table 1, between the inner flame and the outer flame (Examples 1 to 5, Comparative Examples 1 to 5) or the center of the flame ( Comparative Example) The spheroidizing treatment was performed by spraying to 6). The spherical silica powder collected from the gravity sedimentation chamber was sieved, and the acquisition rate and melting rate of particles below 80 μm and the sphericity of particles having a particle size of 45 to 80 μm were measured. The results are shown in Table 1.
[0025]
[Table 1]
Table 1 shows the following.
[0027]
As for the carrier gas flow rate, when it was 15 to 40 m / s, the sphericity was 0.9 or more, the melting rate was 97% or more, and the yield of particles under 80 μm was improved (Examples 1 to 5). On the other hand, if the carrier gas flow rate exceeds 40 m / s, the flame residence time is short, so the melting rate decreases (Comparative Example 2), and if it is less than 15 m / s, the material injection is hindered and the burner As a result, clogging of raw materials frequently occurred, and the yield, sphericity, and melting rate of particles under 80 μm decreased (Comparative Example 1).
[0028]
Regarding the particle size distribution of the silica powder raw material, when the cumulative 10% particle size d10 was less than 10 μm, there were many fine particles, so that the particles were coalesced with the coarse particles, the sphericity decreased, and the enlargement proceeded (Comparative Example 3). In addition, when d90 / d10 exceeded 5 (Comparative Example 4) and when the average particle diameter exceeded 80 μm (Comparative Example 5), the yield of particles under 80 μm significantly decreased.
[0029]
Comparative Example 6 was performed in accordance with Example 4 except that the silica powder raw material was injected into the center of the flame, but only the amount of injection was not performed between the inner flame and the outer flame. The sphericity and melting rate were lower than in Example 4.
[0030]
【The invention's effect】
According to the present invention, a spherical silica powder having a large average particle diameter can be easily produced by increasing its sphericity.
Claims (2)
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| JP06506699A JP3868141B2 (en) | 1999-03-11 | 1999-03-11 | Method for producing spherical silica powder |
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| JP06506699A JP3868141B2 (en) | 1999-03-11 | 1999-03-11 | Method for producing spherical silica powder |
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| JP3868141B2 true JP3868141B2 (en) | 2007-01-17 |
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