In case you missed it.

Emerging Technology

"Photonics Reliability--Managing the Time Bomb"

Author: Professor Nihal Sinnadurai

Abstract: Qualification to photonics reliability "standards" does not provide the evidence required for ensuring the required quality of high-reliability systems. Such products can be time bombs when installed in high-reliability networks. Network survival must therefore be ensured by designing-in system-level fault tolerance. Even where Telcordia or IEC specifications are used, product reliability assurance is best built from practical reliability evidence of building block elements that make up the product. Product reliability solutions require testing related to the reliability risks and thereby to provide the required assurance and quantitative information. Reliability tests are more informative than "qualification," and generate information on reliability behavior, FIT rates and the essential statistics needed by those deploying systems in the field. Additionally, typical qualification tests can generate only crude estimates of high wear-out FIT rates, at levels around 17,000, even if the product has a genuinely low FIT rate, whereas reliability test data yield wear-out FIT rates lower than 500. Random failure FIT rates require genuine field data retrieval, and such observations show that photonics product reliabilities improve with manufacturing maturity. (IPC/JEDEC Global Conference on Lead-Free Reliability and Reliability Testing for RoHS Lead-Free Electronics, April 2007)

Medical Electronics

"Medtech Outsourcing Trends In Singapore"

Author: Susan E. Mucha; [e-mail].

Abstract: Biomedical sciences manufacturing grew to $15 billion in 2006, a 30.2% increase over the prior year. A growing number of large multinational medical OEMs are locating R & D centers or regional headquarters within Singapore because of its strong IP protection laws, skilled labor pool and easy access to a variety of emerging consumer markets. Many medical OEMs also outsource within the region. This paper provides an overview of the medtech industry within Singapore and looks at examples of ways medical OEMs, Singaporean EMS providers and precision engineering suppliers are addressing product development, quality and cost reduction. (SMTA Medical Electronics Symposium, May 2007)

Pb-Free Reliability

"Evaluation of Sn-3.5Ag Based Solder Joint by Ball Impact Test"

Authors: Hiroshi Nishikawa, Kousuke Miki, Tadashi Takemoto

Abstract: In general, Pb-free solders possess more brittle mechanical properties compared with SnPb eutectic, and the thick intermetallic layer at the solder-substrate interface is sensitive to stress and provides sites of initiation and propagation paths for cracks. Therefore, it is important to study the relationship between the interfacial reaction and joint strength using a solder bump. In this study, to evaluate the drop impact reliability of SnAg(Co) solder joint, the impact toughness of the SnAg(Co) solder with a copper pad was investigated by a new ball impact test. Results showed that the fracture along the interface, where intermetallic compounds were formed, was caused by the ball impact test. The ball impact test was found suitable for characterizing the toughness of intermetallic compound at the interface and evaluating reliability after drop impact. (IPC/JEDEC Global Conference on Lead-Free Reliability and Reliability Testing for RoHS Lead-Free Electronics, April 2007)

"Shrinkage Hole Effect on Lead-Free Pin Through-Hole Solder Joint Reliability"

Authors: Christiane Faure, Mark Elkins, Jasbir Bath, Aaron Unterborn, Stephen Mainwaring, Dennis Willie, Xiang Zhou and Doug Watson; [e-mail].

Abstract: This work aimed to determine the effect of shrinkage grooves on wave solder joint reliability. Randomly selected DIPs, connectors and resistors were cross-sectioned from SAC 305 and SnCuNi alloy (and a SnPb control) wave-soldered boards for comparison after 1,654 cycles from -40[degrees] to 125[degrees]C. Shrinkage grooves appeared minimal, with the groove propagation only slightly deeper than the annular ring for both alloys. No significant effect on reliability could be found. No fundamental differences were detected between SAC 305, SnCuNi and SnPb37 PTH wave-soldered joints in terms of solder joint groove formation and propagation during high-temperature range thermal cycling. SAC 305 and SnCuNi PTH solder-joint reliability was comparable to that of SnPb37. Conclusions include: Shrinkage groove formation is typically common for SAC alloys and does not typically exist for SnCuNi and SnPb37. Even if this phenomenon is less pronounced for SnAg3.8Cu0.7 compared to SAC 305, it is not possible to totally avoid them. However, reliability testing has shown them to be benign, and their existence appears to be acceptable. Under high-stress thermal cycling conditions (up to 1,654 cycles -40[degrees], +125[degrees]C), no electrical failure has been attributed to Pb-free wave solder joint failures. Finally, a similar fatigue mode was observed between SAC 305, SnCuNi and SnPb. (IPC/JEDEC Global Conference on Lead-Free Reliability and Reliability Testing for RoHS Lead-Free Electronics, April 2007)

CIRCUITS ASSEMBLY provides abstracts of papers from recent industry conferences and company white papers. With the amount of information increasing, our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.