HERNDON, Va., 24 Dec. 2005. The International Electronics Manufacturing Initiative's (iNEMI) Tin Whisker User Group in Herndon, Va., warns that pure tin electroplating presents a risk in high-reliability applications.
The group also warns that users should be cautious in using tin finishes on alloy 42 (Fe-42Ni) lead-frames in applications where there is significant thermal cycling, and noting possible mitigation practices.
The organization is updating its publication, "Recommendations on Lead-Free Finishes for Components Used in High-Reliability Products," to include changes to some of the group's previous recommendations as well as the addition of new recommendations.
The iNEMI Tin Whisker User Group consists of eight large manufacturers of high-reliability electronic assemblies: Agilent, Alcatel-Lucent, Celestica, Cisco Systems, Delphi Electronics & Safety, Hewlett-Packard, IBM, Sun Microsystems and Tyco Electronics.
The guidelines the group has developed are intended to minimize the risk of failures from tin whiskers. This latest update includes recommendations for component finishes for a variety of applications and reflects the best judgment of the iNEMI User Group members, based on their own experiences and the available data.
"The industry has made significant progress in standardizing its approach to tin whisker mitigation and testing," says Joe Smetana, principal engineer, advanced technology for Alcatel-Lucent, and chair of the iNEMI Tin Whisker User Group.
"Three standards were released in 2005 and 2006 addressing tin whisker testing, environmental acceptance requirements and mitigation practices," Smetana says. "The User Group strongly endorses the use of these documents as part of a comprehensive strategy of mitigation practices, tin whisker testing, and plating process controls, all of which are necessary to reduce the risk of failures associated with tin whiskers."
In other recommendations, the group changed its stance on annealing of matte tin over copper, saying it can be accepted when accompanied by supporting test data; updated its position on bias, noting recent data that indicates electrical bias is no longer considered a significant concern and does not require additional testing; and further clarified statements about the use of tin-bismuth finishes.
The guidelines for migrating to RoHS-compliant finishes has been organized into sections that discuss commonly available mitigation practices, other (less commonly available) practices, finishes that should generally be avoided, mitigation practices that require further study, applications of concern, plus other considerations and recommendations.
The revised recommendations can be downloaded from the iNEMI website at http://thor.inemi.org/webdownload/projects/ese/tin_whiskers/Pb-Free_Finishes_v4.pdf.
For more information contact iNEMI online at www.iNEMI.org.
