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DIRECTIVES & IMPLICATIONS
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Lead is a hazardous substance which, when ingested can be toxic to humans; therefore it has been banned by a European Union directive in an aim to reduce its harmful effects on health and the environment. The ban, which comes into force on July 1st 2006, means that electronic manufacturers must transfer from a tin-lead soldering process to a lead-free process. In recent years the Stokes Research Institute has been addressing the requirements of the electronics industry during this transition.
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LEAD-FREE ACTIVITIES AT SRI
 Manufacturing Optimisation
A research project was completed on lead-free surface mount processing. Screen-printing and reflow process parameters were examined and optimised using Design of Experiments (DoE) techniques for SnAgCu solder pastes and results are available in Stokes publications.
Reliability
As with any new product, once manufacturing issues have been resolved, the long term reliability becomes the most critical aspect i.e. field data, failure modes, performance in specific environments. These topics are continually under investigation at SRI.
Application-Specific Solder Alloys
More fundamental reliability challenges are being encountered due to the design of novel miniaturised, higher performance multifunctional electronics. This is due the fact that more powerful functions are required in smaller and thinner products and along with the employment of lead-free materials which increases the complexity of the interconnection metallurgy. SRI are currently running a number of research projects in the area of application-specific solder alloys. As data is obtained from field returns and from reliability testing (impact, torsion, humidity-corrosion, high current), new lead-free interconnect technologies (solder + metallisation) are being developed for specific applications such as impact tolerance or high current.
Consultancy
SRI provides a reliability testing and consultancy service which includes the following:
 Process characterisation
Solder joint evaluation
PCB and component evaluations
Specialised analytical techniques such as SEM/EDAX, FIB, TEM
Contamination testing
IPC tests
Vibration testing
Vendor approvals
Accelerated temperature cycling (ATC)
Detailed technical reports and feedback on test results are provided with follow-up company visits and process audits available where required.
Industrial Links/Collaborations
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ELFNET
ELFNET (European Lead Free soldering NETwork) is a European research network of the national organisations, technical experts and industry bodies in micro-electronics. It provides a platform to coordinate, integrate and optimise research, enabling electronics producers in the EU to meet an EU directive to introduce lead-free soldering by July 1st 2006. ELFNET operates in 19 European countries and is funded by the European Commission. SRI is a core member of the Reliability Technical Expert Group (TEG).
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SMART Group
The SMART Group (Surface Mount and Related Technologies Group) is the leading European technical trade association representing the electronics manufacturing industry. SRI presents at the many seminars run regularly by the group's Irish branch on the topic of lead-free manufacturing.
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| E-Learning
SRI have developed an e-learning course which gives an introduction to lead-free soldering. The course is aimed at making Irish companies aware of lead-free issues and is available free of charge from Claire Ryan.
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