Authored By:
Denis Barbini - BCS, Nottingham, NH, USA
Denis Jean - Plexus, Inc., Neenah, WI, USA
Stuart Longgood - Delphi Corporation, Kokomo, IN, USA
Keith Howell - Nihon Superior, Cadmenton, MO, USA
Jian Miremadi - Hewlett-Packard Company, Palo Alto, CA, USA
Summary
Today's wave soldering processes solder electronic assemblies within the large eutectic tin lead processing window. The issues surrounding the conversion to lead free assembly are multiple and varied. Logistics, cost, material selection, and equipment choices/options are some of these challenges that require planning and organization.
However, at the core of lead free assembly is soldering. The iNEMI lead free wave soldering team embarked on a multi-tiered project that focuses specifically on two aspects: identifying the impact of critical parameters on the development of a reliable, robust lead free wave soldering process as well as characterizing the performance of the electrical interconnect.
While previous investigations of lead free wave soldering as well as standards development focused on process optimization, material selection, through-hole fill, coverage requirements, few, published investigations focused on the reliability of both SMD and Through-Hole solder joints assembled with various board finishes and thicknesses, component types, and alloys. This iNEMI collaboration studied and is reporting on identifying the impact of critical parameters on the development of a reliable, robust lead free wave soldering process as well as determining the behavior and performance of the various solder joints.
The team specifically designed a test vehicle for testing the norms of tin lead wave soldering and to address component and board types specific to various industries. The result of this investigation is to provide the electronics industry valuable information pertaining to the relationship between through-hole penetration and solder joint performance as a function of thermal cycling, and subsequent failure analysis.
Overall, this investigation looks to bring an understanding of how critical wave soldering parameters correlate to performance and provide the reader with the information necessary to make educated decisions in selecting process parameters, material sets, and acceptability standards.
Conclusions
This research provides insight into several of the key questions and challenges observed in today's lead free wave soldering process. The iNEMI lead free wave soldering team embarked on a multi-tiered project that focuses specifically on two aspects: Identifying the impact of critical parameters on the development of a reliable, robust lead free wave soldering process and determining the process that achieves the optimized soldered joint.
This collaborative effort investigated the relationship of board design factors to through-hole penetration and joint integrity/performance. Addressed in this study are inspection criteria, failure definition and measurement, followed by root cause analysis and ultimately optimized process confirmation. The result of this investigation was to lay the foundation of a broader effort to characterize the performance of through-hole solder joints on a test vehicle specifically designed for testing the norms of tin lead wave soldering.
Overall, this investigation looks to bring an understanding of how critical wave soldering parameters influence the various outputs. It also attempts to provide the reader with the information necessary to make educated decisions in selecting board attributes and materials in this ever changing environment. It is critical to understand, identify and control various process parameters in order to execute a rational implementation strategy for a reliable and robust lead free wave soldering process that results in the highest quality product.
Initially Published in the SMTA Proceedings
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