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HERNDON, Va. The International Electronics Manufacturing Initiative's (iNEMI) tin whisker user group updated its "Recommendations on Lead-free Finishes for Components Used in High-reliability Products," revising and adding recommendations.
The user group under the consensus that pure-tin electroplating presents a risk in high-reliability applications outlines methods to reduce risk of failure caused by tin whiskers. New recommendations cover corrosion, mechanical stress, tin-over-brass and tin-over-steel, thermal cycling, and non-columnar grain structures. Discussions of bright tin includes formal recommendations regarding use, and other updates.
The group changed its stance on annealing matte-tin over copper, finding this process acceptable when accompanied by sufficient supporting test data. Electrical bias will no longer be considered a significant concern by the group. Information on alloy 42 (Fe-42Ni) compelled the group to suggest caution when using tin finishes on alloy 42 leadframes in applications facing high thermal cycling. The group also clarified recommendations on tin-bismuth finishes, and reorganized the document to be more user-friendly.
Recommendations are available for download on the iNEMI Website. The user group comprises eight manufacturers of high-reliability electronic assemblies: Agilent, Alcatel-Lucent, Celestica, Cisco Systems, Delphi Electronics & Safety, Hewlett-Packard, IBM, Sun Microsystems, and Tyco Electronics.