Reliability of Lead Free Solder
Summary A predictive model of lead-free solder joint reliability is being developed based on empirical experimentation of a manufacturing process. The current manufacturing status in relation to the usage, constraints, defect rates and reliability problems associated with the use of a lead-free solder process. A predictive model for the reliability of lead free solder joints based on joint characteristics, solder technology and characteristics of the manufacturing reflow process. Finally the resulting predictive model for solder joint reliability will be integrated with manufacturing process simulated data. This is part of a larger ATRP project involving the NMCR (UCC) and UL.
The Research Team
Dr. John Donovan Principal Researcher Department of Engineering, IT, Sligo. Mr. Shane O’Neill Research Student Department of Engineering, IT, Sligo.
Background
Comparatively little is known of the reliability characteristics of lead-free soldering. It is not possible to simply substitute a lead-free solder into an existing lead based solder process. Higher reflow temperatures are required for lead-free soldering and the effect this has on component reliability is unknown. Interface issues also become a concern as some lead-free alloys have a greater tendency to dissolve copper than others. Lead-free soldering requires alternative component surface metallizations, flux composition, and alternative PCB materials. All these factors leads to unknown reliability characteristics of the final solder joint.
Project Details
To determine the current manufacturing status in relation to the usage, constraints, defect rates and reliability problems associated with the use of a lead-free solder process.
To develop a predictive model for the reliability of lead-free solder joints based on joint characteristics, solder technology and characteristics of the manufacturing reflow process. This work will be conducted on the AMT manufacturing line in the University of Limerick and will involve extensive experimental design work. Screening designs will initially be utilised to identify the appropriate factors for detailed experimentation.
To integrate the resulting predictive model for solder joint reliability with the simulation and stress analysis results developed by UL using finite element analysis. This will provide a more detailed and comprehensive reliability model.
To validate the results achieved from the predictive reliability model with the reliability results achieved from a volume manufacturing process. Field failure returns will be analysed and a model comparison will be conducted.