Instability of the Wetting Tip in Lead-Free Solder Reactions

9705195 Tu本研究的目的是研究无铅焊料在薄膜金属化中的润湿行为。重点研究了焊接过程中的润湿尖端行为和金属间化合物的形成。研究了一种独特的薄膜反应，在这种反应中，颗粒成熟并剥落，导致去湿。为了了解反应润湿的基本原理及其在电子封装薄膜金属化中的应用，研究的重点有两个：(1)反应润湿针尖的不稳定性；(2)剥落和脱湿的机理。研究了稀铅(锡)合金中锡的成分与润湿角的关系。铅(锡)在镍上的润湿角变化将小于铅(锡)在铜上的润湿角变化，而铅(锡)在钯上的润湿角变化又将远小于铅(锡)在钯上的润湿角变化。前人的工作表明，熔融共晶SnPb对Pd的润湿角是不稳定的，且随时间变化。对镍、铜、钯表面进行了系统的对比研究。焊锡技术对电子封装至关重要。半导体工业协会(SIA)预测，在设备制造中越来越多地使用焊料。然而，美国国会和环境投影机构(EPA)表达了对电子行业使用铅的担忧。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. ***