JP4045033B2

JP4045033B2 - Method for producing fine tin powder

Info

Publication number: JP4045033B2
Application number: JP28509998A
Authority: JP
Inventors: 健三塙; 和明高橋
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 1998-10-07
Filing date: 1998-10-07
Publication date: 2008-02-13
Anticipated expiration: 2018-10-07
Also published as: JP2000119708A

Description

【０００１】
【発明の属する技術分野】
本発明は、経済性に優れ、簡便、かつ高収率の微小スズ粉末の製造方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
近年、電子機器の配線基板の小型化に伴い表面実装の技術が急速に発展した。とりわけ、実装技術の中心となっているマイクロソルダリング技術もますます高度化している。この表面実装の時にはハンダペーストを用いるが、このハンダペーストに対する要求も厳しいものとなってきており、ハンダ粉も微細化のものが要求されている。
【０００３】
従来、ハンダ粉としては、スズ−鉛系ハンダが一般的であり、平均粒径２０〜４０μｍ程度のものが用いられているが、パッドサイズが２５〜１００μｍやパッドピッチが２５〜５０μｍという微細な回路基板パターンの要求もあり、これに対応するためには２０μｍ未満の微細粉末であるハンダ粉を使用する必要がある。
【０００４】
このため、ハンダ粉に用いられるスズ粉末としても平均粒径５〜７μｍ程度の微小粉末が要求されている。このようなスズの微小粉末を得るために、例えばアトマイズ粉を分級することが考えられるが、歩留まりが極めて悪く、経済性に劣る。また、このような微小粉末のスズを得るために、水アトマイズ法によっても可能であるが、装置的に大規模となり、トータル的には非常に高コストとなってしまう。
【０００５】
従って、本発明の目的は、簡便で経済性に優れ、しかも高収率の微小スズ粉末の製造方法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者らは、検討の結果、高純度のスズ地金又は粉末をα化した後、衝突板式粉砕機で粉砕することによって、上記目的が達成し得ることを知見した。
【０００７】
本発明は、上記知見に基づきなされたもので、純度９９．９５重量％以上のスズ地金又は粉末を−３０〜−５０℃でα化させた後、衝突板式粉砕機で粉砕することを特徴とする微小スズ粉末の製造方法を提供するものである。
【０００８】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明では、純度９９．９５重量％以上のスズ地金又は粉末を用いる。この地金は、例えばスズを鋳造することによって得られる。スズ粉末は上記地金を溶融し、これをアトマイズすることにより得られる。このアトマイズ粉末の平均粒径は、２０〜５０μｍ程度である。
【０００９】
このスズ地金又は粉末の純度は、上記のように９９．９５重量％以上であり、純度がこれ未満であり、不純物を多く含有するとスズのα化が阻害される。特に、鉛、ビスマス、アンチモンを不純物として多く含有した場合には、スズのα化が阻害される。また、上記スズ地金又は粉末に、ケイ素及び／又はゲルマニウムを含有させることによって、スズのα化を促進することができる。このようなケイ素及び／又はゲルマニウムの含有量は、スズ地金又は粉末に対して、０．５重量％以下、好ましくは０．０１〜０．５重量％である。
【００１０】
本発明では、このスズ地金又は粉末を−３０〜−５０℃でα化させる。スズにはβ型とα型の２つの同素体がある。一般的なスズは密度７．２８ｇ／ｃｍ³のβ型（正方晶）で白色錫と呼ばれている。他方の密度５．８０ｇ／ｃｍ³のα型（立法晶）は灰色錫と呼ばれ特殊な環境下、例えば極寒地でなければ見ることはできない。α型スズはβ型から転移する際に密度差による体積膨張を伴うために脆化する。本発明では、上記β型のスズ地金又は粉末を−３０〜−５０℃で３〜１０日保持することによってα化させる。
【００１１】
本発明では、このようにα化させたスズを粉砕し、微小化する。粉砕には、衝突板式粉砕機を用いる。このような衝突板式粉砕機としては、エバラトリアードジェット（ＰＭ型、荏原製作所社製）、ＩＤＳ式ジェットミル（ＩＤＳ−２型、日本ニューマチック工業社製）等が挙げられる。
【００１２】
このスズ地金又は粉末のα化、粉砕は、所定の粒径、すなわち平均粒径５〜７μｍになるまで１回或いは数回繰り返し行なわれる。このようにして、平均粒径５〜７μｍの微小スズ粉末が得られる。
【００１３】
この微小スズ粉末は、ハンダ粉、特にファインピッチ用のハンダ粉の材料として好適に使用できる。
【００１４】
【実施例】
以下、実施例等に基づき本発明を具体的に説明する。
【００１５】
＜α型転移に対するスズ地金の影響＞
〔試験例１〕
純度９９．９９重量％以上のスズ地金を溶解鋳造し、直径２０ｍｍ、厚さ５ｍｍの円盤状の試料を作製した。これを−４０℃の冷凍庫に保持し、β型からα型へ転移する様子を観察した。１日経過後、試料表面に紫色の点状の隆起物（ｗａｒｔｓと呼ばれるα型スズの初期痕跡）が数点観察された。その後、α型スズは点状の隆起物を基点にして全体に広がっていき、４日経過後には全体がα型に転移して崩壊した。
【００１６】
〔試験例２〕
試験例１と同様の純度９９．９９重量％以上のスズ地金を溶解し、これに０．０５重量％のゲルマニウムを添加して鋳造し、直径２０ｍｍ、厚さ５ｍｍの円盤状の試料を作製した。試料を−４０℃の冷凍庫に保持して観察した。α型の初期痕跡が認められるまで０．５日、全体がα型に至って崩壊するまで２日であった。これによりα型への転移に対して、促進元素としてのゲルマニウムの有効性が確認された。ゲルマニウムの結晶構造はα型スズと同じ等軸晶系のダイヤモンド構造を持ち、ゲルマニウムが種となってα型への転移が促進される。
【００１７】
〔試験例３〕
試験例２と同様に、純度９９．９９重量％以上のスズ地金を溶解し、これにゲルマニウムと同じ等軸晶系のダイヤモンド構造を持つケイ素を０．０５重量％添加した試料を作製し、−４０℃の冷凍庫に保持して観察した。α型の初期痕跡が認められるまで０．５日、全体がα型に至って崩壊するまで３日で、ゲルマニウムと同様にケイ素の有効性も確認された。
【００１８】
〔試験例４〕
試験例１〜３に用いたのと同様の純度９９．９９重量％以上のスズ地金をガスアトマイズ法によりアトマイズ粉を作製した。これを透明なラミネート袋に充填して真空に密封した後、−４０℃の冷凍庫に保持した観察した。２日経過後、銀白色のガスアトマイズ粉の中に紫に近い灰色の変色域が点在していることが認められた。６日経過後には、充填したアトマイズ粉全量の変色が認められた。この変色したアトマイズ粉は、Ｘ線回折パターンによりα型スズであることが確認された。
【００１９】
〔比較試験例１〕
試験例１の円盤状試料を−２０℃の冷凍庫に保持して観察した。α型の初期痕跡が認められるまで１１日、全体がα型に至って崩壊するまで３０日で、−４０℃の保持と比較してα型への転移が遅くなった。
【００２０】
〔比較試験例２〕
純度９９．９０重量％のスズ地金を溶解鋳造し、直径２０ｍｍ、厚さ５ｍｍの円盤状の試料を作製した。これを−４０℃の冷凍庫に保持して観察した。３２日経過後にα型スズの初期痕跡が数点観察されたが、その後の転移の進行は非常に緩やかで、１年以上経過しても全体がα型スズに転移して崩壊するには至らなかった。
【００２１】
〔比較試験例３〕
比較試験例２と同様の純度９９．９０重量％以上のスズ地金に、試験例２と同様に、０．０５％のゲルマニウムを添加して円盤状の試料を作製した。これを−４０℃の冷凍庫に保持して観察した。２０日経過後にα型スズの初期痕跡が数点観察されたが、その後の転移の進行は非常に緩やかで、１年以上経過しても全体がα型スズに転移して崩壊するには至らなかった。
【００２２】
〔比較試験例４〕
９９．９０重量％スズ地金から試験例４と同様にガスアトマイズ法によりアトマイズ粉を作製した。試験例４と同様に透明なラミネート袋に充填して真空に密封した後、−４０℃の冷凍庫に保持した観察した。１年以上経過しても銀白色を保ったままでα型への転移は認められなかった。
【００２３】
これら試験例１〜４及び比較試験例１〜４の結果等を表１に示すと共に、純度９９．９９重量％以上のスズ地金及び純度９９．９０重量％のスズ地金の不純物含有量を表２に示す。
【００２４】
【表１】

【００２５】
【表２】

【００２６】
＜微小スズ粉末の製造＞
〔実施例１〕
試験例４で得られた平均粒径３５．７μｍのアトマイズ粉を用い、α化、粉砕及び分級を下記の通り行った。
（第１回α化）
上記アトマイズ粉を透明なラミネート袋に充填し、真空包装して−４０℃で８日保持した。
（第１回粉砕）
衝突板式粉砕機としてエバラトリアードジェット（ＰＭ型、荏原製作所社製）を用いた。この粉砕機は、衝突板による粉砕と旋回による摩擦粉砕を組み合わせた乾式粉砕機である。供給圧力６．５ｋｇ／ｃｍ²、旋回圧力４．０ｋｇ／ｃｍ²、原料供給速度１．０ｋｇ／ｈで粉砕を行った。その結果、回収率は９９％、回収品の平均粒径は１５．９μｍであった。
（第２回α化）
第１回粉砕で得られた平均粒径１５．９μｍの回収品を−４０℃で３日保持した。
（第２回粉砕）
第１回粉砕と全く同様にして粉砕を行った。その結果、回収率は９８％、回収品の平均粒径は８．５６μｍであった。
（分級）
分級機として、ＭＤＳセパレーター（ＭＤＳ−１３０型、日本ニューマチック工業社製）を用い、供給速度５ｋｇ／ｈで分級を行った。その結果、分級後の微粉の歩留りは５９％、平均粒径は６．１３μｍ、出発原料であるアトマイズ粉からの歩留りは５７％であった。
【００２７】
〔実施例２〕
試験例４で得られた平均粒径３５．７μｍのアトマイズ粉を用い、α化及び粉砕を下記の通り行った。
（第１回α化）
上記アトマイズ粉を透明なラミネート袋に充填し、真空包装して−４０℃で８日保持した。
（第１回粉砕）
衝突板式粉砕機としてＩＤＳ式ジェットミル（ＩＤＳ−２型、日本ニューマチック工業社製）を用いた。この粉砕機は、優れた粉砕力と精密な分級機構を有する衝突板式粉砕機である。供給圧力６．０ｋｇ／ｃｍ²、原料供給速度４．５ｋｇ／ｈで粉砕を行った。その結果、回収率は８９％、回収品の平均粒径は１５．６μｍであった。
（第２回α化）
第１回粉砕で得られた平均粒径１５．６μｍの回収品を−４０℃で３日保持した。
（第２回粉砕）
第１回粉砕と全く同様にして粉砕を行った。その結果、回収率は５５％、回収品の平均粒径は５．２６μｍ、出発原料であるアトマイズ粉からの歩留りは４９％であった。
【００２８】
〔実施例３〕
純度９９．９９重量％のスズ地金塊を用い、α化、粉砕及び分級を下記の通り行った。
（第１回α化）
上記スズ地金塊を−４０℃で１４日保持した。この結果、スズ地金塊は粒状或いは針状の粒子にまで崩壊した。崩壊後の粒度は１６メッシュオーバー１％、１６〜１００メッシュ９０％、１００メッシュアンダー９％であった。
（第１回粉砕）
実施例１の第１回粉砕と同一の粉砕機、粉砕条件で粉砕を行った。その結果、回収率は９８％、回収品の平均粒径は５０．９μｍであった。
（第２回α化）
第１回粉砕で得られた平均粒径５０．９μｍの回収品を−４０℃で３日保持した。
（第２回粉砕）
第１回粉砕と全く同様にして粉砕を行った。その結果、回収率は９６％、回収品の平均粒径は１４．００μｍであった。
（分級）
実施例１の分級と同一の分級機、分級条件で分級を行った。その結果、分級後の微粉の歩留り３７％、平均粒径５．４９μｍ、スズ地金からの歩留り３５％であり、スズ地金塊からでも微小スズ粉を製造することが可能となった。
【００３０】
〔比較例１〕
試験例４で得られた平均粒径３５．７μｍのアトマイズ粉を用い、分級のみを下記の通り行った。
（分級）
実施例１の分級と同一の分級機、分級条件で分級を行った。その結果、分級後の微粉の歩留り０．６％、平均粒径６．０８μｍであり、歩留りが極端に悪かった。
【００３１】
〔比較例２〕
試験例４で得られた平均粒径３５．７μｍのアトマイズ粉を用い、粉砕のみを下記の通り行った。
（第１回粉砕）
実施例１の第１回粉砕と同一の粉砕機、粉砕条件で粉砕を行った。その結果、回収率は７５％、回収品の平均粒径は３７．１μｍであり、β型スズのままでは延性があり粉砕による微細化は起こらず、逆にスズ粉末同志の付着による粒径の増大が起きた。
【００３２】
〔比較例３〕
試験例４で得られた平均粒径３５．７μｍのアトマイズ粉を用い、α化、粉砕及び分級を下記の通り行った。
（第１回α化）
上記アトマイズ粉を透明なラミネート袋に充填し、真空包装して−４０℃で８日保持した。
（第１回粉砕）
粉砕機としてシングルトラックジェットミル（ＦＳ−４型、セイシン企業社製）を用いた。この粉砕機は、粒子の相互衝突と相互摩擦による乾式粉砕機で、衝突板式粉砕機ではない。供給圧力７．４ｋｇ／ｃｍ² 、原料供給速度０．８５ｋｇ／ｈで粉砕を行った。その結果、回収率は５５％、回収品の平均粒径は１５．９μｍであった。
（第２回α化）
第１回粉砕で得られた平均粒径１５．９μｍの回収品を−４０℃で３日保持した。
（第２回粉砕）
第１回粉砕と全く同様にして粉砕を行った。その結果、回収率は３０％、回収品の平均粒径は８．５６μｍであった。
（分級）
実施例１の分級と同一の分級機、分級条件で分級を行った。その結果、分級後の微粉の歩留り５９％、平均粒径６．１３μｍ、出発原料であるアトマイズ粉からの歩留りは１０％であった。この粉砕機においては、粉砕室に供給されたα型スズ粉末は、瞬間的には微細化されるが、粒子相互の衝突と摩擦を継続的に受けるために直ぐにβ型に戻ってしまう。β型に戻ったスズ粉末は、それ以上の微細化は起こらず、逆に粗大化が進行して粉砕機内に留まって回収率の低下を招くことになる。
【００３３】
【発明の効果】
以上説明したように、本発明の製造方法によって、簡便で経済性に優れ、しかも高収率で微小スズ粉末が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing fine tin powder that is excellent in economic efficiency, simple and high yield.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, with the miniaturization of wiring boards of electronic devices, surface mounting technology has rapidly developed. In particular, micro soldering technology, which is the center of packaging technology, is becoming increasingly sophisticated. Solder paste is used for this surface mounting, but the demand for this solder paste is becoming severe, and the solder powder is required to be finer.
[0003]
Conventionally, tin-lead solder is generally used as the solder powder, and one having an average particle diameter of about 20 to 40 μm is used, but the fine pad size is 25 to 100 μm and the pad pitch is 25 to 50 μm. There is also a demand for a circuit board pattern, and in order to meet this requirement, it is necessary to use solder powder which is a fine powder of less than 20 μm.
[0004]
For this reason, a fine powder having an average particle size of about 5 to 7 μm is also required as a tin powder used for solder powder. In order to obtain such tin fine powder, for example, it is conceivable to classify atomized powder, but the yield is extremely poor and the economy is poor. Further, in order to obtain such fine powder tin, it is possible by the water atomization method, but the scale becomes large in terms of apparatus, and the total cost becomes very high.
[0005]
Accordingly, an object of the present invention is to provide a method for producing a fine tin powder which is simple and excellent in economic efficiency and has a high yield.
[0006]
[Means for Solving the Problems]
As a result of the study, the present inventors have found that the above object can be achieved by converting a high-purity tin metal or powder into α and then pulverizing it with a collision plate pulverizer.
[0007]
The present invention has been made on the basis of the above findings, and is characterized in that a tin metal or powder having a purity of 99.95% by weight or more is alphatized at -30 to -50 ° C and then pulverized by a collision plate pulverizer. A method for producing a fine tin powder is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In the present invention, tin metal or powder having a purity of 99.95% by weight or more is used. This metal is obtained, for example, by casting tin. Tin powder is obtained by melting the above-mentioned metal and atomizing it. The average particle size of the atomized powder is about 20 to 50 μm.
[0009]
As described above, the purity of this tin metal or powder is 99.95% by weight or more, and the purity is less than this. In particular, when a large amount of lead, bismuth, and antimony are contained as impurities, the alpha conversion of tin is inhibited. Moreover, alpha-ization of tin can be accelerated | stimulated by making the said tin ingot or powder contain silicon and / or germanium. The content of silicon and / or germanium is 0.5% by weight or less, preferably 0.01 to 0.5% by weight, based on tin metal or powder.
[0010]
In the present invention, this tin metal or powder is pregelatinized at -30 to -50 ° C. Tin has two allotropes, β-type and α-type. General tin is β-type (tetragonal) with a density of 7.28 g / cm ³ and is called white tin. On the other hand, the α-type (legislative crystal) with a density of 5.80 g / cm ³ is called gray tin and cannot be seen unless it is in a special environment, for example, in a cold region. α-type tin becomes brittle because it undergoes volume expansion due to density difference when it transitions from β-type. In the present invention, the β-type tin ingot or powder is gelatinized by holding at −30 to −50 ° C. for 3 to 10 days.
[0011]
In the present invention, the tin that has been pregelatinized in this way is pulverized and miniaturized. An impact plate type pulverizer is used for pulverization. Examples of such a collision plate pulverizer include an Ebara triad jet (PM type, manufactured by Ebara Seisakusho Co., Ltd.), an IDS type jet mill (IDS-2 type, manufactured by Nippon Pneumatic Industrial Co., Ltd. ), and the like .
[0012]
The tin metal or powder is pregelatinized and pulverized once or several times until a predetermined particle size, that is, an average particle size of 5 to 7 μm. In this way, fine tin powder having an average particle size of 5 to 7 μm is obtained.
[0013]
This fine tin powder can be suitably used as a material for solder powder, particularly for fine pitch.
[0014]
【Example】
Hereinafter, the present invention will be specifically described based on examples and the like.
[0015]
<Effect of tin bullion on α-type transition>
[Test Example 1]
A tin metal having a purity of 99.99% by weight or more was melted and cast to prepare a disk-shaped sample having a diameter of 20 mm and a thickness of 5 mm. This was held in a freezer at −40 ° C., and the state of transition from β type to α type was observed. After 1 day, several purple dot-like ridges (initial traces of α-type tin called “warts”) were observed on the sample surface. Thereafter, the α-type tin spreads from the point-like raised matter to the whole, and after 4 days, the whole changed to the α-type and collapsed.
[0016]
[Test Example 2]
A tin metal having a purity of 99.99% by weight or more similar to that of Test Example 1 is dissolved, 0.05% by weight of germanium is added thereto, and cast to prepare a disk-shaped sample having a diameter of 20 mm and a thickness of 5 mm. did. The sample was held in a freezer at −40 ° C. and observed. It was 0.5 days until the initial trace of α-type was observed, and 2 days until the whole reached α-type and collapsed. This confirmed the effectiveness of germanium as an accelerating element for the transition to α-type. The crystal structure of germanium has the same equiaxed diamond structure as that of α-type tin, and germanium serves as a seed to promote the transition to α-type.
[0017]
[Test Example 3]
In the same manner as in Test Example 2, a tin metal having a purity of 99.99% by weight or more was dissolved, and a sample having 0.05% by weight of silicon having the same equiaxed diamond structure as germanium added thereto was prepared. Observation was carried out by holding in a -40 ° C freezer. The effectiveness of silicon was confirmed as well as germanium in 0.5 days until the initial trace of α-type was observed and 3 days until the whole reached α-type and collapsed.
[0018]
[Test Example 4]
Atomized powder was produced by a gas atomization method using a tin metal having a purity of 99.99% by weight or more similar to that used in Test Examples 1 to 3. This was filled in a transparent laminate bag and sealed in a vacuum, and then observed in a freezer at −40 ° C. After two days, it was confirmed that grayish discoloration areas near purple were scattered in the silver-white gas atomized powder. After 6 days, discoloration of the filled atomized powder was observed. This discolored atomized powder was confirmed to be α-type tin by an X-ray diffraction pattern.
[0019]
[Comparative Test Example 1]
The disk-shaped sample of Test Example 1 was observed while being held in a -20 ° C freezer. 11 days until the initial trace of α-type was observed, and 30 days until the whole reached α-type and disintegrated, and the transition to α-type was delayed as compared with -40 ° C retention.
[0020]
[Comparative Test Example 2]
A tin metal having a purity of 99.90% by weight was melt-cast to produce a disk-shaped sample having a diameter of 20 mm and a thickness of 5 mm. This was held in a freezer at −40 ° C. and observed. Several initial traces of α-type tin were observed after the passage of 32 days, but the subsequent progress of the transition was very slow, and even after a year or more, the whole transitioned to α-type tin and collapsed. There wasn't.
[0021]
[Comparative Test Example 3]
In the same manner as in Test Example 2, 0.05% germanium was added to a tin metal having a purity of 99.90% by weight or more similar to Comparative Test Example 2 to prepare a disk-shaped sample. This was held in a freezer at −40 ° C. and observed. Several initial traces of α-type tin were observed after 20 days, but the progress of the subsequent transition was very slow, and even after a year or more, the whole had transformed into α-type tin and collapsed. There wasn't.
[0022]
[Comparative Test Example 4]
Atomized powder was produced from 99.90% by weight tin in the same manner as in Test Example 4 by the gas atomization method. In the same manner as in Test Example 4, the sample was filled in a transparent laminate bag and sealed in a vacuum, and then observed in a freezer at −40 ° C. Even after 1 year or more, the transition to α-type was not observed while maintaining the silver white color.
[0023]
The results of these Test Examples 1 to 4 and Comparative Test Examples 1 to 4 are shown in Table 1, and the impurity content of tin bullion having a purity of 99.99 wt% or more and tin bullion having a purity of 99.90 wt% is shown. It shows in Table 2.
[0024]
[Table 1]

[0025]
[Table 2]

[0026]
<Manufacture of fine tin powder>
[Example 1]
Using the atomized powder having an average particle size of 35.7 μm obtained in Test Example 4, pregelatinization, pulverization, and classification were performed as follows.
(First alpha)
The atomized powder was filled in a transparent laminate bag, vacuum packaged, and held at −40 ° C. for 8 days.
(1st grinding)
An Ebara triad jet (PM type, manufactured by Ebara Seisakusho) was used as a collision plate type pulverizer. This pulverizer is a dry pulverizer that combines pulverization by a collision plate and friction pulverization by swirling. Supply pressure 6.5 kg / cm ^2, turning pressure 4.0 kg / cm ^2, was triturated with feeding rate 1.0 kg / h. As a result, the recovery rate was 99%, and the average particle size of the recovered product was 15.9 μm.
(2nd alpha)
A recovered product having an average particle diameter of 15.9 μm obtained by the first pulverization was held at −40 ° C. for 3 days.
(2nd grinding)
Grinding was performed in exactly the same way as the first grinding. As a result, the recovery rate was 98%, and the average particle size of the recovered product was 8.56 μm.
(Classification)
As a classifier, an MDS separator (MDS-130 type, manufactured by Nippon Pneumatic Industry Co., Ltd.) was used, and classification was performed at a supply rate of 5 kg / h. As a result, the yield of fine powder after classification was 59%, the average particle size was 6.13 μm, and the yield from atomized powder as a starting material was 57%.
[0027]
[Example 2]
Using the atomized powder having an average particle diameter of 35.7 μm obtained in Test Example 4, the gelatinization and pulverization were performed as follows.
(First alpha)
The atomized powder was filled in a transparent laminate bag, vacuum packaged, and held at −40 ° C. for 8 days.
(1st grinding)
An IDS jet mill (IDS-2 type, manufactured by Nippon Pneumatic Industry Co., Ltd.) was used as a collision plate type pulverizer. This crusher is a collision plate type crusher having an excellent crushing force and a precise classification mechanism. Grinding was performed at a supply pressure of 6.0 kg / cm ² and a raw material supply speed of 4.5 kg / h. As a result, the recovery rate was 89%, and the average particle size of the recovered product was 15.6 μm.
(2nd alpha)
The recovered product having an average particle diameter of 15.6 μm obtained by the first pulverization was kept at −40 ° C. for 3 days.
(2nd grinding)
Grinding was performed in exactly the same way as the first grinding. As a result, the recovery rate was 55%, the average particle size of the recovered product was 5.26 μm, and the yield from the atomized powder as the starting material was 49%.
[0028]
Example 3
Using a tin ingot with a purity of 99.99% by weight, pregelatinization, pulverization and classification were performed as follows.
(First alpha)
The tin bullion was held at −40 ° C. for 14 days. As a result, the tin metal block collapsed into granular or acicular particles. The particle size after disintegration was 16% over 1%, 16-100 mesh 90%, 100 mesh under 9%.
(1st grinding)
The pulverization was performed using the same pulverizer and pulverization conditions as those in the first pulverization of Example 1. As a result, the recovery rate was 98%, and the average particle size of the recovered products was 50.9 μm.
(2nd alpha)
The recovered product having an average particle diameter of 50.9 μm obtained by the first pulverization was held at −40 ° C. for 3 days.
(2nd grinding)
Grinding was performed in exactly the same way as the first grinding. As a result, the recovery rate was 96%, and the average particle size of the recovered product was 14.00 μm.
(Classification)
Classification was performed using the same classifier and classification conditions as those used in Example 1. As a result, the yield of fine powder after classification was 37%, the average particle size was 5.49 μm, and the yield was 35% from tin bullion, making it possible to produce fine tin powder even from tin bullion.
[0030]
[Comparative Example 1]
Using the atomized powder having an average particle size of 35.7 μm obtained in Test Example 4, only classification was performed as follows.
(Classification)
Classification was performed using the same classifier and classification conditions as those used in Example 1. As a result, the yield of fine powder after classification was 0.6% and the average particle size was 6.08 μm, and the yield was extremely bad.
[0031]
[Comparative Example 2]
Using the atomized powder having an average particle size of 35.7 μm obtained in Test Example 4, only grinding was performed as follows.
(1st grinding)
The pulverization was performed using the same pulverizer and pulverization conditions as those in the first pulverization of Example 1. As a result, the recovery rate is 75%, the average particle size of the recovered product is 37.1 μm, and the β-type tin is ductile and does not become finer by pulverization. An increase occurred.
[0032]
[Comparative Example 3]
Using the atomized powder having an average particle size of 35.7 μm obtained in Test Example 4, pregelatinization, pulverization, and classification were performed as follows.
(First alpha)
The atomized powder was filled in a transparent laminate bag, vacuum packaged, and held at −40 ° C. for 8 days.
(1st grinding)
A single track jet mill (FS-4 type, manufactured by Seishin Enterprise Co., Ltd.) was used as a pulverizer. The grinder is a dry pulverizer through mutual collision and mutual friction of the particles, not an impact plate type pulverizing machine. Grinding was performed at a supply pressure of 7.4 kg / cm ² and a raw material supply rate of 0.85 kg / h. As a result, the recovery rate was 55%, and the average particle size of the recovered product was 15.9 μm.
(2nd alpha)
A recovered product having an average particle diameter of 15.9 μm obtained by the first pulverization was held at −40 ° C. for 3 days.
(2nd grinding)
Grinding was performed in exactly the same way as the first grinding. As a result, the recovery rate was 30%, and the average particle size of the recovered product was 8.56 μm.
(Classification)
Classification was performed using the same classifier and classification conditions as those used in Example 1. As a result, the yield of fine powder after classification was 59%, the average particle size was 6.13 μm, and the yield from atomized powder as a starting material was 10%. In this pulverizer, the α-type tin powder supplied to the pulverization chamber is instantaneously refined, but immediately returns to the β-type in order to continuously receive collision and friction between particles. The tin powder that has returned to the β-type is not further refined, and conversely, coarsening proceeds and remains in the pulverizer, leading to a reduction in the recovery rate.
[0033]
【The invention's effect】
As explained above, the production method of the present invention provides a simple and excellent economic efficiency and a fine tin powder with a high yield.

Claims

A method for producing fine tin powder, characterized in that tin metal or powder having a purity of 99.95% by weight or more is alphatized at -30 to -50 ° C and then pulverized by a collision plate pulverizer.

The manufacturing method of the fine tin powder of Claim 1 which repeats the said gelatinization and grinding | pulverization.

Method for producing a fine tin powder according to claim 1 or 2, wherein said tin ingots or powder has a silicon and / or germanium .01 to 0.5 wt.% Free.

The method for producing fine tin powder according to claim 1, 2 or 3, wherein the average particle size is 5 to 7 µm.