【作者】 李颖；

【导师】 董伟；

【作者基本信息】 大连理工大学 ， 材料学， 2012， 硕士

【摘要】 均匀球形微米级粒子是一种特殊的球形粉末颗粒,具有广泛的应用空间。无论是直接将微粒子应用在BGA电子封装、球形半导体等方面,还是利用产生的液滴实现净成形及快速沉积等领域,都要求其具有粒径均匀、圆球度高、粒径可控以及热履历一致等特点。而传统的微粒子制备方法,如切丝打孔重熔法、雾化法以及均匀液滴成型法等都有或多或少的缺点,不能满足上述应用领域的使用要求。因此本文旨在进行原理上的创新,研制出能够实现按需喷射的均匀球形微粒子制备设备。本工作研制了脉冲小孔低温喷射设备,包括以下几大组成部分：均匀液滴产生系统、加热冷却系统、差压控制系统、压电陶瓷驱动系统以及粒子收集和真空系统等。利用该低温设备制备出了均匀球形的63Sn-37Pb共晶成分的微粒子,探讨了工艺参数对粒径大小及分散程度的影响。并对高温设备制备出的Fe-Co基金属玻璃合金微粒子进行了评价,讨论了该成分合金获得全玻璃相的临界冷却速率。通过研究,得到以下结论：自主开发的低温设备可以稳定制备粒径均匀、圆球度高、表面质量好、晶粒细小且满足BGA精密封装要求的63Sn-37Pb的微粒子；所制备粒子的大小及分散程度和工艺参数,如压电陶瓷两端施加的脉冲信号的波形、电压大小、频率以及熔池和腔体的压力差等关系密切；使用孔径为200gm的小孔制备63Sn-37Pb微粒子的最优参数组合为：选用梯形波作为压电陶瓷的驱动信号,波形的电压范围为90-120V,梯形波的上升时间为250μs,保持和下降时间各为1000μs,频率为10-200Hz,熔池和腔体的压力差范围为2-3torr；利用脉冲小孔喷射法高温设备可在纯He和50%Ar+50%He混合气氛下制备出不同粒径的,且粒径均匀、圆球度高的[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4金属玻璃微粒子；在纯He和50%Ar+50%He混合气氛下制备出的全玻璃相粒子的临界尺寸分别为645μm和515μm,任何气氛条件下,随着粒径的减小,所制备的微粒子的微观结构由全结晶相向金属玻璃相与结晶相的混合相最终向完全玻璃相转变；该方法制备[(Fe0.5Co0.5)o.75Bo.2Si0.05]96Nb4金属玻璃单分散粒子的临界冷却速率为800-1100K/s,不随气体的改变而改变。更多还原

【Abstract】 Mono-sized spherical micro particles are a special kind of spherical powder particles, which have a wide application. As for various applications, not only the particles applied directly in BGA electronic packaging, spherical semiconductor and so on, but also droplets used in net-form manufacture, rapid deposition and so on, all the particles or droplets prepared by different methods are required to be with characteristics of narrow size distribution, high sphericity, particle size controllable and the identical cooling history. While, the traditional preparation methods of micro particles, such as Cutting Punching Remelting Method, Atomization, Uniform Droplet Spray Method (UDS) have more or less faults, and cannot meet the requirements of the above application fields. Therefore, this work aims to innovate in principle, and consequently develop a new kind of equipment used for preparing mono-sized spherical particles with the desired size.The main parts of independently developed low temperature POEM, including uniform droplets generating system, heating and cooling system, pressure difference controlling system, piezoelectric actuator driving system, particles collecting system, vacuum system and etc., have been introduced in this paper. Spherical and mono-sized micro particles of63Sn-37Pb eutectic composition have been prepared by above low temperature equipment. The effects of technological parameters on the particle size and size distribution are discussed. Furthermore, characterization for Fe-Co based metallic glass alloy particles prepared by high temperature POEM is carried out, and critical cooling rate to realize fully crystalline phase is also estimated. Based on results and discussion, some conclusions can be drawn in the following.63Sn-37Pb micro particles with the characterization of narrow size distribution, high sphericity, good surface quality and fine grains can be stably prepared by independently developed low temperature POEM. The obtained micro particles meet requirements of the BGA packaging. Technological parameters, such as the pulse signal waveform applied to piezoelectric actuator, applied voltage, frequency and pressure difference between the crucible and chamber, have important effects on particle size and size distribution. With the orifice size of200μm, the optimal parameters applied in preparation of63Sn-37Pb particles is as followed:trapezoidal wave is selected as driving signal for piezoelectric actuator; the applied voltage ranges from90V to120V; the time to reach the pulse voltage from zero (tup) is set as250μs, and the holding time (thold) and the time to return back from pulse voltage to zero (tfall) are both1000μs; frequency of piezoelectric actuator motion ranges from10Hz to200Hz; the applied pressure, which is the difference between the pressure in the crucible and chamber is adjusted within the range of2-3torr.[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4metallic glass alloy particles of different particle size with narrow size distribution and high sphericity were separately prepared by high temperature POEM in He or50%Ar+50%He atmosphere, respectively. The particles obtained in the fully glassy phase have a diameter of less than645μm in He atmosphere and less than515μm in50%Ar+50%He atmosphere. The phase transitions of particles from the fully crystalline phase to the mixed phase which was mixture of the glassy phase and the crystalline phase to the fully glassy phase occurred as the particle diameter is decreased regardless of any atmosphere. Critical cooling rate for fully glassy phase of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4metallic glass alloy particles prepared by POEM is estimated to be within the range of800-1100K.sec-1. No changes of the critical cooling rate occur in any atmosphere.更多还原