Journal of SMT Article

ISSUES AND SOLUTIONS TO IMPLEMENTING LEAD FREE SOLDERING

Author: Lee Whiteman
Company: American Competitiveness Inst.
Date Published: 10/1/2000   Volume: 13-4

Abstract: Environmental issues have effected the methods used in electronics manufacturing. The Clean Air Act of 1990 and the Montreal Protocol eliminated the use of chlorinated flourocarbons (CFC solvents), which traditionally were used to clean electronics hardware. New cleaning technologies (aqueous and semi-aqueous cleaning) and new soldering technologies (low residue / no clean soldering) were developed and implemented as a direct result of this legislation.

Currently, new pending environmental legislation in Europe and Asia will require electronics manufacturers to eliminate lead from soldering. The impact of lead-free solders is much wider than the effects caused by CFC elimination. CFC elimination concentrated primarily on the cleaning processes. Lead is a major constituent in tin-lead solder alloys currently being used. These alloys are used everywhere in electronics manufacturing from individual components and boards through hand soldering, wave soldering, and reflow soldering.

Alternative lead-free solder alloys are being developed, but their introduction into electronics manufacturing requires major changes to current manufacturing processes, electronic components, and inspection requirements. Lead-free solder alloys generally require higher temperatures, up to 260 degrees Celsius as opposed to 215 degress Celsius, to perform the soldering operation, which may effect the reliability of boards and components. Soldering equipment may not be capable of maintaining such high temperatures. The temperature profiles employed in reflow soldering may be longer, which will adversely impact productivity. Material compatibility issues, when employing lead-free soldering technologies on heritage lead-based assemblies, are a serious concern. Certain alloys, when used on a component or board coated with lead-tin solder, will form intermetallics which will reduce the resulting solder joint's mechanical integrity. As a result of issues similar to these mention, one can conclude that there are no drop-in, "turnkey", lead-free solder alternatives available.

The objective of this paper is to identify the issues pertaining to implementing lead-free solders in electronics manufacturing. While several electronics manufacturers are generating plans to implement, or have implemented lead-free soldering technologies, the vast majority of electronics manufacturers have not. This paper will discuss the manufacturing process variables and component variables associated with the implementation of lead-free soldering processes.



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