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February 2015 • SMT Magazine 79 TIN WHISKer rISK aSSeSSMeNT OF a TIN SurFaCe FINISHed CONNeCTOr continues tiation/growth is somewhat isolated from ad- jacent leads by the configuration of the con- nector plastic housing (Figure 11). While the plastic housing configuration does not com- pletely isolate adjacent leads, it does signifi- cantly reduce the view factor, which describes how likely a whisker growing from one surface will make contact with another surface, there- by further mitigating the risks of tin-whiskers induced failure. Conclusions The solder charge connector was found to be in compliance with the JESD201 Class 2 ac- ceptance criteria in accordance with modified JESD201 test parameters used. The investigation data, including SEM assessment of reflow sol- dered connectors, indicates that the tin whisker risk is extremely low for the component. Prod- uct design teams should be aware that the tin whisker risk is not zero and some segments of high-performance customer base may not ac- cept the connector in their designs due to the lack of zero risk. It is recommended that for an extreme environment, long-life application, a program should consider customizing parts with gold plating on the solder tail in place of the standard matte tin finish. acknowledgements The authors would like to thank Corey Bryant, Component Application Engineering CAMEL Laboratory, for outstanding SEM analy- sis efforts. SMT references 1. D. Hillman, et al, "JCAA/JG-PP No-Lead Solder Project: -55ºC to +125ºC Thermal Cycle Testing Final Report," Rockwell Collins Work- ing Paper WP06-2021, October 2006. 2. "Tin Whiskers: A History of Documented Electrical System Failures, A Briefing Prepared for the Space Shuttle Program Office," Dr. Hen- ning Leidecker/NASA Goddard, Jay Brusse/QSS Group, Inc. April 2006. 3. "Evaluation of Conformal Coatings for Future Spacecraft Applications," B.D. Dunn, European Space Agency document ESA SP1173, August 1994. 4. GEIA-STD-0005-2, Standard for Mitigat- ing the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems, Sec- tion C.2.2.4 Conformal Coat or Foam Encap- sulation Over Whisker-Prone Surfaces, Govern- ment Electronics and Information Technology Association (GEIA), June 2006. 5. Web Site: NASA Experiment 2. 6. Tin Whisker Risk Factors, David Pinsky, Michael Osterman, and Sanka Ganesan, IEEE Transaction on Components and Packaging Technologies, Vol. 27, No. 2, June 2004. 7. D. Hillman, "An Assessment of Tin Whis- ker Risk Mitigation Resulting from Standard Soldering Processing of Surface Mount Chip Re- sistor Components," Rockwell Collins Working Paper WP05-2027, 2005. 8. T. Hester, "Tin Whiskers Self-Mitigation in Surface Mount Components Attached with Leaded (Pb-Containing) Solder Alloys, 7 th Inter- national Symposium on Tin Whiskers, Novem- ber, 2013. 9. D. Hillman, et al, "High I/O BGA Connec- tor Solder Joint Integrity Investigation," SMTAI Conference, October, 2014. 10. JEDEC Standard, JESD201, "Environ- mental Acceptance Requirements for Tin Whis- ker Susceptibility of Tin and Tin Alloy Surface Finishes," March 2006. 11. S.J. Meschter, "SERDP Tin Whisker Test- ing and Modeling: Simplified Whisker Geomet- ric Short Circuit Risk Model Development," 8 th International Symposium on Tin Whiskers, Oc- tober 29, 2014, Raleigh, NC. Note: This paper was presented at the 2014 IPC/ CALCE International Symposium on Tin Whiskers. David Hillman is a principal materials and process engineer in the advanced operations engineering Department at rockwell collins inc. ross Wilcoxon is a research and development engineer with more than 15 years of experience in mechanical packaging of electron - ics used in harsh environments. Feature

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