SGER: High Temperature Pb-Free Joints for Flip Chip Technology

这项由材料研究部授予加州大学的探索性研究(SGER)小额赠款是为了研究取代高铅焊点的新方法。通过设计无铅共晶锡银铜(SnAgCu)焊料与钯(Pd)的超快反应，可以形成具有工业加工要求的高熔点的钯锡化合物金属间化合物接头。在250℃的温度下，通过回流步骤可以形成金属间化合物接头，在250℃下形成接头后，它不会在250℃下熔化。创新的概念是，在形成金属间接头的过程中，使用了共晶SnAgCu焊料和Pd之间的超快速反应，并在250℃下在短短几分钟内形成了50到100微米的接头。形成后，就没有焊料了。由于这种类型的接头以前没有被研究过，这被认为是一个高风险的项目。出于对环境的担忧，目前有四项反铅法案在美国国会待决。其中一个来自环境保护局(EPA)。欧盟已经通过了一项法律，在2006年7月1日之前禁止在电子产品中使用铅。在大型计算机中，已使用高熔点(300摄氏度以上)高铅(97Pb3Sn)焊料将硅片连接到陶瓷模块。美国国家电子制造倡议(NEMI)建议用共晶SnAgCu焊料替代低温共晶SnPb焊料，但目前还没有无铅焊料来替代较高温度的97Pb3Sn焊料。为此，美国大型计算机公司获得了美国环保局的豁免，可以继续使用高铅焊料制造到2010年。这种情况下，迫切需要开发一种高温无铅焊料。对这一问题的研究可能会影响我们信息技术的未来，并增强美国在全球高端技术竞争中的领导地位。从教育角度来看，SGER项目支持两名国内学生，其中包括一名女学生。

This small grant for exploratory research (SGER) award by the Division of Materials Research to University of California is to study new approaches to replace high lead solder joints. By designing an ultra-fast reaction between the lead-free eutectic Tin-Silver-Copper (SnAgCu) solder and Palladium (Pd), an intermetallic joint of Palladdium-Tin compound can be formed that has the high melting point required by industrial processing. The intermetallic joint can be formed by a reflow step at a temperature of 250o C, and after the joint is formed, it will not melt at 250o C. The innovative concept is that in forming the intermetallic joint an ultra-fast reaction between eutectic SnAgCu solder and Pd is used and a joint of 50 to 100 micron size is formed at 250o C in just a few minutes. After formation, there no solder left. Since this type of joint has not been studied before, this is considered to be a high-risk project. Due to environmental concerns, there are four anti-lead bills pending in the US Congress. One of them is from the Environmental Protection Agency (EPA). The European Union has already passed a law to ban the use of lead in electronic products by July 1, 2006. In mainframe computers, a high melting point (above 300o C) high-lead (97Pb3Sn) solder has been used to connect silicon chips to ceramic modules. The National Electronic Manufacturing Initiative (NEMI) has recommended eutectic SnAgCu solder to replace low temperature eutectic SnPb solder, but there is no lead-free solder available to replace the higher temperature 97Pb3Sn solder. For this reason, the US mainframe computer companies have obtained an exemption from the EPA to continue the use of high-lead solder in manufacturing until 2010. This situation has resulted in an urgent need to develop a high temperature lead-free solder. Research on this problem could impact the future of our information technology and enhance US leadership in global competition in high-end technology. From an educational point of view, the SGER project supports two domestic students, including a female student.