Metallurgical Reliability Issues in Flip Chip Technology

9987484Tu这项研究是一个系统的，基本的研究焊点的可靠性进行了机械，化学和电力的组合。该项目研究了电子封装技术中最具挑战性的可靠性问题之一。电迁移是在SnPb和无铅焊料从室温到150 ℃测量。电迁移对界面反应的影响是在焊点界面处确定的。还研究了应力对电迁移的影响。倒装芯片焊点的耐久性的综合效果进行检查。在这些研究的基础上，应开发洞察力，这将使有用的解决方案，以提高焊点的可靠性。在消费电子产品和微处理器中，目前的趋势是将硅芯片直接附着到有机基板上。智能卡就是一个很好的例子。它被称为直接芯片附着或倒装芯片技术，其中使用焊料凸块的区域阵列将芯片连接到衬底。这是一种低成本工艺，它提供了封装高性能芯片所需的大量电引线（超过几千条）。然而，芯片和有机衬底之间的热膨胀系数的非常大的差异导致热应力，这可能产生严重的可靠性问题。由于基板的有机性质，需要使用低熔点焊料，例如共晶SnPb或共晶SnAg（无Pb）合金。这些高锡焊料与芯片表面上的凸块下薄膜金属化反应非常快，导致机械上非常弱的接头。此外，对于未来的ULSI芯片，焊料凸块的尺寸可以接近50微米。 然后，由于焊料在环境温度附近具有快速的原子扩散率，因此电迁移成为一个问题。

9987484TuThis research is a systematic, basic study of the reliability of solder joints undergoing a combination of mechanical, chemical and electrical forces. The project examines one of the most challenging reliability issues in electronic packaging technology. Electromigration is measured in SnPb and Pb-free solders from room temperature to 150C. The effect of electromigration on interfacial reactions is determined at the solder joint interfaces. Also studied is the effect of stress on electromigration. The combined effects are examined on the durability of a flip chip solder joint. On the basis of these studies, insight should be developed that will enable useful solutions to enhancing solder joint reliability. %%%In consumer electronic goods as well as in microprocessors, the current trend is to attach the silicon chip directly to an organic substrate. Smart card is a good example. It is called direct chip attachment or flip chip technology in which an area array of solder bumps is used to join the chip to the substrate. This is a low cost process, which offers the large number of electrical leads (over a few thousands) required for packaging a high performance chip. However, the very large difference in coefficients of thermal expansion between the chip and the organic substrate results in thermal stresses that can create a serious reliability issue. Owing to the organic nature of the substrate, the use of a low melting point solder such as eutectic SnPb or eutectic SnAg (Pb-free) alloy is needed. These high-Sn solders react extremely fast with the under-bump thin film metallization on the chip surface, resulting in mechanically very weak joints. Furthermore, for future ULSI chips, the size of the solder bump could approach 50 microns. Then electromigration becomes a concern since the solder has a fast atomic diffusivity near ambient temperature.***