摘要本课题主要研究了功率超声制备Sn-Bi合金球粒工艺的优化。Sn-Bi无铅焊料由于绿色无污染、熔点低等优点，公认为是Sn-Pb焊料的理想替代材料，近些年来也得到广泛研究。因为超声空化效应，熔体在液相线上即能大量生核，而超声声流效应将形成的晶核散发到整个熔体。功率超声使得层片状共晶组织更明显，晶粒细化。微粒尺寸随施振功率增大而减小并随针孔尺寸减小而减小，冷却后获得粒径均一、圆球度好、表面光洁度高Sn-Bi合金球粒。87109

本实验的工艺优化结果表明：（1）使用恒温加热金属液，颗粒均匀度由0。65提高到0。91，滴落量由23颗/min提高到108颗/min；（2）使用针孔喷射，颗粒平均直径减小，颗粒平均直径由1。37mm降低到0。98mm；（3）使用梯度式油冷，成球率由0。61提高到0。89。

毕业论文关键词：功率超声处理；共晶；针孔喷口；梯度油冷。

Abstract This paper studies the power ultrasonic preparation Sn-Bi alloy pellets Optimization 。Sn-Bi lead-free solder because of its green pollution-free, and low melting point, is recognized as the Sn-Pb solder ideal alternative materials, has also been extensively studied in recent years。Because of ultrasonic cavitation, the melt in the liquid line that is able to a large number of nucleation, and nuclei formed ultrasonic acoustic streaming effect distributing the entire melt。Power ultrasound makes lamellar eutectic more obvious grain refinement。 Particle size decreases with vibrating power increases and decreases with the pinhole size reduction to obtain a uniform particle size after cooling, good sphericity, surface finish Sn-Bi alloy pellets。Process optimization results of this experiment showed that: (1) constant heating the liquid metal can improve the uniformity of the particles from the o。65 to 0。91,dropping to improve capacity from 23  per minute to 108 per minute。 (2) using a pinhole jet that allows the average particle diameter is reduced,the average diameter of the particles is reduced from 1。37mm to 0。98 mm。 (3) using a gradient-type oil cooler ,belling rate from 0。61 up to 0。89。

 Key words: power ultrasonic treatment; eutectic; pinhole vents; gradient oil cooler。

目 录

第一章  绪论 1

1。1 目前无铅焊料的发展 1

1。1。1目前无铅焊料的研究 1

1。1。2 BGA封装中Sn-Bi合金的实际应用 2

1。2 在细晶中功率超声的应用 2

1。3 制备球状Sn-Bi合金颗粒的方法 3

1。4 目前存在问题与展望 4

1。5 本文研究的内容与目的 5

第二章  原始实验工艺 6

   2。1实验装备 6

2。1。1超声波发生装置与变幅杆 6

2。1。2工作支架 7

2。1。3石墨坩埚和碳钢片 7

2。1。4冷却装置 8

   2。2合金制备 8

   2。3实验工艺 9

2。3。1 功率超声 9

2。3。2 微孔喷射 10

2。3。3 冷却 10

   2。4实验结果分析