SMTA International Conference Proceedings


LEAD CONTAMINATION RISKS IN LEAD FREE SOLDER JOINTS FOR HIGH TEMPERATURE APPLICATIONS

Author: Mark Privett et al.
Company: Henkel Loctite Electronics
Date Published: 9/26/2004   Conference: SMTA International


Abstract: Legislation in Europe and Japan will require electronic assembly manufacturers to switch to lead free solders by mid-2006. An industry wide effort has been made to develop and qualify alternative solder alloys for lead free assemblies. Meanwhile, component manufacturers have been slower to move away from tin-lead terminations. For some high temperature applications, in which the operating temperatures of the assemblies are close to 170°C, high lead content high temperature alloys have been used.

Since the melting point of the preferred lead free alloys tin-silvercopper (SAC) alloys is 217°C they offer the possibility of a single product for both low and high operating temperature assemblies. Although there have been numerous studies on the reliability of lead-free alloys, there are still questions regarding their suitability for high temperature applications particularly where lead contamination will occur [1-3]. This paper focuses on a case study in which failures occurred in solder joints produced from tin-lead terminated components and SAC387 (Sn 3.8Ag 0.7Cu) lead free solder.

A cross functional team including the component manufacturer, solder paste manufacturer, and the board assembler was established to investigate the failure and through classical problem solving techniques identify, and eliminate the root cause of the failures. This paper will present an overview of the problems observed in order to provide a better understanding of potential pitfalls of this material combination.

Key Words: Pb-Free, Lead Contamination, High temperature solder.



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