Instability of the Wetting Tip in Lead-Free Solder Reactions

9705195屠本研究的目的是研究无铅焊料在薄膜金属化过程中的润湿行为。重点是在焊接过程中润湿尖端的行为和金属间化合物的形成。研究了一种独特的薄膜反应，其中颗粒成熟并脱落导致脱湿。为了了解反应性润湿的基础科学及其在电子封装金属化薄膜中的应用，本研究的两个主要主题是：(1)反应性润湿尖端的不稳定性；(2)剥落和脱湿的机制。研究了润湿角对稀铅（锡）合金中锡成分的影响。预计Pb（Sn）在Ni上的润湿角变化将小于Pb（Sn）在Cu上的润湿角变化，而Cu上的润湿角变化将远远小于Pb（Sn）在Pd上的润湿角变化。以往的研究表明，熔融的共晶SnPb在Pd上的润湿角是不稳定的，并随时间变化。对Ni、Cu和Pd表面进行了系统的比较研究。焊料技术对电子封装至关重要。半导体工业协会（SIA）预测了器件制造中焊料使用增加的趋势。然而，美国国会和环境规划署（EPA）对电子工业中铅的使用表示担忧。因此，需要对无铅焊料及其工艺、性能和可靠性进行研究。＊＊＊

9705195 Tu It is the purpose of this research to investigate the wetting behavior of Pb-free solders on thin film metallization. Emphasis is on the wetting tip behavior and intermetallic compound formation during soldering. Investigated is a unique thin film reaction where the grains ripen and spall resulting in dewetting. To understand the basic science of reactive wetting and the applications to thin film metallization in electronic packaging, two main topics are the focus of the research: (1) the instability of a reactive wetting tip and (2) the mechanisms of spalling and dewetting. The dependence of wetting angle on the composition of Sn in dilute Pb(Sn) alloys is examined. It is expected that the wetting angle changes observed in the case of Pb(Sn) on Ni will be less than that of Pb(Sn) on Cu, which, in turn, will be much less than that of Pb(Sn) on Pd. Previous work shows that the wetting angle of molten eutectic SnPb on Pd is unstable and changes with time. A systematic and comparative study on Ni, Cu, and Pd surfaces is conducted.. %%% Solder technology is essential for electronic packaging. The Semiconductor Industry Association (SIA) has projected a trend of increasing use of solder in device manufacturing. The US Congress and Environmental Projection Agency (EPA), however, has expressed a concern over the use of Pb in the electronics industry. As a consequence, lead (Pb)-free solders and their processes, properties and reliability need to be studied. ***