Joe You comments are correct... Whiskers are very hard to see visually, maybe no one is really looking for them. They are also very fragile, They can break off and the casuse is gone. i suspect they are right behind dendrites on the Prateo chart. i was involved in a Space Failure caused by a tin whisker on a Terminal. i have seen lots of them... Paul Signorelli Reliability Engineer >>> [log in to unmask] 04/17/03 10:08AM >>> Some of our component suppliers have notified us that they will be changing some lead finishes to pure tin. We suspect that this may be the beginning of a landslide, and as a high-rel supplier, we have to consider the risk of shorting from tin whiskers. Until about a decade ago, we used a lot of parts with tin finish, and never saw a whisker, at least that we know of. Whiskers appear to be rare, but the risk does not seem to be well understood, or at least quantifiable. Maybe they're lost within the noise of normal component failures. Technical literature has some anecdotes and a few interesting pictures, and there are suggestions on possible causes (stresses within the plating or from lead forming), and mitigations (e.g. matte tin is better than bright acid tin, conformal coat is good). What we don't seem to have is anything that a reliability engineer could use to allow comparison of risks and benefits. One easy reaction would be to hot-solder dip the leads, but this will be expensive, and there is a finite probability of damage from the extra handling, ESD, moisture exposure, and the heat cycle. Maybe we could anneal the parts after plating or lead forming, or even the whole assembly after soldering. Don't know what temperatures or bake times would be needed to anneal pure tin. I'm posting here instead of a lead-free forum because because this is going to affect us all, whether we use tin/lead solder or not. And even with the dwindling membership, the jokes are better. Joe Kane BAE SYSTEMS Platform Solutions Johnson City, NY --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------