本文關(guān)鍵詞： Al-Bi Al-Bi-Sn 核殼型 凝固 相分離 表面偏析　出處：《上海交通大學(xué)》2011年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著電子產(chǎn)品向“輕、薄、短、小”及多功能方向發(fā)展,先進(jìn)封裝技術(shù)向著小型化、高密度和細(xì)間距方向演進(jìn),因此,焊球的導(dǎo)電性和散熱性不足、易產(chǎn)生封裝缺陷等問題日益突出。一個(gè)較好的解決辦法是采用以高強(qiáng)高導(dǎo)電高熔點(diǎn)材料為核心的核殼型焊球,但因目前此類焊球主要采用電鍍法制備,因此其應(yīng)用受到嚴(yán)重制約。本文研究了Al-Bi-(Sn)偏晶合金的相分離和凝固行為,探討了核殼組織的形成和影響機(jī)理,獲得了Al@Sn-Bi核殼型球粒及其一步法制備工藝,為核殼型金屬顆粒包括電子封裝用焊球的制備和應(yīng)用奠定了基礎(chǔ)。 首先,針對Al-Bi二元體系,采用射流斷裂法研究了合金成分、過熱度、硅油溫度、液滴飛行距離和液滴尺寸的影響。結(jié)果表明,由于表面偏析,不同成分的Al-Bi合金顆粒殼層總是由富Bi相組成。顆粒有圓環(huán)型和月食型核殼兩種形貌。通過ANSYS軟件模擬液滴的溫度場,并計(jì)算第二相小液滴的運(yùn)動(dòng)速率,發(fā)現(xiàn)只有當(dāng)冷卻速度和溫度梯度精確地配合,才會(huì)使Marangoni和Stokes運(yùn)動(dòng)速率相平衡,從而能獲得圓環(huán)型核殼組織。對于Al-65.5Bi (in wt.%)合金,當(dāng)熔體過熱度為100 K,液滴自由飛行距離為3 mm,硅油為常溫時(shí),直徑0.9 mm左右的顆粒基本能獲得圓環(huán)型核殼形貌,否則易獲得月食型核殼形貌。根據(jù)上述分析,總結(jié)并圖解了Al-Bi合金的凝固路徑和核殼形貌的形成過程。此外,還發(fā)現(xiàn)核殼型Al-65.5Bi合金球粒的整體與內(nèi)核直徑滿足關(guān)系式:Dcore=0.9137 Dparticle-0.0312,線性相關(guān)度為0.96。 其次,對于Al-Bi-Sn合金,研究了7種成分,發(fā)現(xiàn)成分點(diǎn)位于液相難混溶區(qū)內(nèi)和邊界上都易于獲得核殼形貌。隨著過熱度降低和硅油溫度提高,顆粒由三層變成兩層同心和兩層偏心核殼形貌。對于(Al34.5Bi65.5)67.8Sn32.2合金顆粒,當(dāng)過熱度為100 K,飛行距離為30 mm,硅油溫度為283-473 K時(shí),易形成完好核殼組織。其殼層由Sn-Bi基合金組成,熔化范圍為407-431 K,符合低溫?zé)o鉛焊料的熔化溫度要求;其核層由Al-Sn基合金組成,熔化溫度為823-844 K左右,有利于提高導(dǎo)電導(dǎo)熱性并在封裝過程中保證共面性。通過示差掃描量熱儀研究了Al-Bi-Sn合金的相變行為,并結(jié)合能譜分析和電鏡觀察,總結(jié)并圖解了Al-Bi-Sn合金的凝固路徑和核殼組織形成過程。
[Abstract]:With the development of electronic products in the direction of "light, thin, short, small" and multifunction, advanced packaging technology has evolved towards miniaturization, high density and fine spacing. Therefore, the electric conductivity and heat dissipation of solder balls are insufficient. A better solution is to adopt core-shell solder ball with high strength and high conductivity and high melting point material as the core, but at present, this kind of solder ball is mainly prepared by electroplating. Therefore, its application is seriously restricted. The phase separation and solidification behavior of Al-Bi-nn monotectic alloy are studied, and the formation and influence mechanism of core-shell microstructure are discussed. The Al@Sn-Bi core-shell spherical particles and their one-step preparation process were obtained, which laid a foundation for the preparation and application of core-shell metal particles, including solder balls for electronic packaging. Firstly, the effects of alloy composition, superheat, silicone oil temperature, droplet flying distance and droplet size on Al-Bi binary system were investigated by jet fracture method. The particle shell of Al-Bi alloy with different composition is always composed of Bi-rich phase. The particles have two morphologies: annular and lunar eclipse core-shell. The temperature field of droplets is simulated by ANSYS software. The moving rate of the second phase droplet is calculated. It is found that the velocity of Marangoni and Stokes will be balanced only when the cooling rate and temperature gradient are matched accurately. The circular core-shell structure can be obtained. For the Al-65.5Bi alloy, the free flying distance of the droplet is 3 mm when the melt superheat is 100K. When the silicon oil is at room temperature, the core-shell morphology of ring type can be obtained basically by the diameter of 0.9 mm particles, otherwise it is easy to obtain the core-shell shape of lunar eclipse type. The solidification path and core-shell morphology of Al-Bi alloy were summarized and illustrated. It is also found that the whole core diameter of core-shell Al-65.5Bi alloy is equal to the kernel diameter of 0.9137 Dparticle-0.0312. The linear correlation was 0.96. Secondly, for the Al-Bi-Sn alloy, 7 compositions were studied. It was found that the core-shell morphology was easily obtained in the liquid phase inmiscible region and at the boundary, with the decrease of superheat and the increase of the temperature of silicon oil. The particles changed from three layers to two layers of concentric and two layers of eccentric core-shell morphologies. For Al34.5Bi65.5A67.8Sn32.2 alloy particles, the superheat was 100K. When the flying distance is 30 mm and the temperature of silicon oil is 283-473 K, it is easy to form perfect core-shell structure. The shell layer is composed of Sn-Bi base alloy and melting range is 407-431 K. Meet the melting temperature requirements of low temperature lead-free solder; The nuclear layer is composed of Al-Sn base alloy and the melting temperature is about 823-844K. The phase transformation behavior of Al-Bi-Sn alloy was studied by differential scanning calorimeter (DSC) and observed by EDS and electron microscope. The solidification path and core-shell structure formation process of Al-Bi-Sn alloy were summarized and illustrated.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2011
【分類號(hào)】：TG146.21

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