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September 2014 • The PCB Magazine 29 why should there be a need to test and rework? The simple fact is that most electronic assem- bly problems are related to the inherent weak- ness of the soldering process and solder joints failure remains a leading cause especially when there is shock or vibration [10] . Moreover, below 0.5 mm lead pitch, which is where the com- ponent roadmap trends are headed, assembly yields drop off appreciably, even with multiple preassembly inspection steps implemented and/or applied. The EMS industry has come to accept the weakness of its assembly and clean- ing processes even as it strives to constantly im- prove them, making marginal improvements through new materials and equipment and as a result has come to also expect that rework and repair are a natural part of the manufac- turing process. This acceptance carries with it what can be best described as a self-defeating ingrained attitude and results in the manufac- turing having to continually carry out a process that might otherwise be made unnecessary. In short, if the components are fully tested and burned-in and the processes used are properly controlled, the final product should be high- yielding, provided the design is inherently val- id and robust. The limits of reliability of future electronic products could well be better defined by IC reliability than the reliability of the cir- cuits and plated vias that are used to intercon- nect them. Conclusion The aluminum circuit structures as have been described in this article are simple to design and eminently possible to manufac- ture. They can be easily produced using well- established manufacturing infrastructure tools, equipment and processing techniques which are simply reordered to make highly useful elec- tronic products suitable for use in everything from consumer to high-reliability automotive, military and aerospace products. The limits are likely to be defined more by the imagination of the designer than the limits of the fundamental technology which has been described. Acknowledgment The author humbly acknowledges the sup- port of the members of the Verdant Electronics Advisory Board, who have offered their unwav- ering encouragement and sound advice for the last seven years. PCB References 1. Fjelstad, J. "Reversing the Electronic As- sembly Process," Semiconductor International, Vol 32 No. 13 pp 24–28, December 2009. 2. Fjelstad, J. "Environmentally friendly as- sembly of robust electronics without solder," Circuit World, Vol. 34 Iss: 2, pp.27–33 2008. 3. W. Callister and D. Rethwisch, Appendix C, Fundamentals of Materials Science and En- gineering, an Integrated Approach. 3 rd Edition. Wiley (2007). 4. Lowry, R., "Counterfeit Electronic Com- ponents – An Overview," Oneida Research Ser- vices. 5. Lee, D., "What Can No Longer Be Ignored In Today's Electronic Designs," SMTA Chapter Meeting Presentation, Jan 2008. 6. Engelmaier, W., "Reliability Issues for Printed Circuit Boards in Lead-Free Soldering" SMTA Presentation Archive. 7. Karavakis, K and Bertling, S, "Conductive Anodic Filament (CAF): The Threat to Miniatur- ization of the Electronics Industry," MEPTEC Journal, Number 4, pp 24-27, 2004. 8. NASA Metal Whiskers website. 9. Buonpastore, P., "Survey: RoHS Costs at Over $32 Billion," PC Design and Manufactur- ing Magazine, April 2008. 10. de Maio, D. "High-frequency vibration tests of Sn-Pb and lead-free solder joints," Pro- ceedings IEMRC/TWI Technical Seminar: De- velopments in Interconnection, Assembly and Packaging, December 2008. Verdant electronics founder and president Joseph (Joe) fjel- stad is a four-decade veteran of the electronics industry and an international authority and in- novator in the field of electron- ic interconnection and packaging technolo- gies. fjelstad has more than 250 u.s. and international patents issued or pending and is the author of Flexible Circuit Technology. ALuMINuM BASE CIRCuIT TECHNOLOGy continues