In Japan most companies are moving towards Sn-Bi lead finishes (typically Sn-2Bi), with the NiPdAu finish (traced to Texas Instruments) commonly in second place, and some companies accepting coarse grained matte Sn. It has been reported that the Bi succeeds in eliminating whisker concerns, while it is generally recognized that matte Sn directly on the Cu-based leadframe removes most but not all concerns. In Europe, the popular finish is coarse grained matte Sn over Ni on leadframe to avoid the Cu-Sn intermetallics commonly thought to be a source of localized stress thought to be a prime driver for whisker growth. Bi as a lead finish is a possible concern while Pb remains on boards or is present as a contaminant in solder waves. The Sn-Pb-Bi eutectic melting temperature is approximately 98 Celsius. It is thought that concentration of this ternary liquid phase during cooling of solders with a reasonably wide pasty range can occur due to the sweeping of this phase away from solidification fronts, due to low solubility, during cooling to result in concentration of this material at the interface with the hottest, or slowest cooling solder joint interface. The NiPdAu finish avoids all of these problems, but is the most expensive, and not all companies can transfer mold to leadframes with an external Au surface (however thin) and achieve good Pb-Free MSL ratings. Leo ------------------------------------ Leo M. Higgins III, Ph.D. ASAT Inc. Central Region Mgr. / Director of Sales [log in to unmask] 3755 Capital of Texas Hwy-So Suite 100 Austin, TX USA 78726 tel: 512-383-4593 fax: 512-383-1590 mobile: 512-423-2002 ------------------------------------ -----Original Message----- From: Guenter Grossmann [mailto:[log in to unmask]] Sent: Thursday, January 22, 2004 10:14 AM To: [log in to unmask] Subject: [TN] Antw: [TN] Lead-free Component Finishes James 1) BGA's SnAgCu Passive : Sn looks like the candidate specially since the whisker problem seems to be about to be solved IC's: Sn or PaAu 2) BGA's: You can solder SnAgCu balls with SnPb. However, one can observe Pb contamination along the grain boundaries. Dave Surarski reported early failures due to that. I couldn't say jet. We are testing. All the other components can be soldered with SnPb without a problem. 3) Military is excluded of RoHS (at the moment). What do you mean with commercial? Look for the RoHS in the web. I don't know the address but Google finds it easy if you look for RoHS. Best regards Guenter EMPA Swiss Federal Laboratories for Materials Testing and Research Centre for Reliability Guenter Grossmann, Senior Engineer 8600 Duebendorf Switzerland Phone: xx41 1 823 4279 Fax : xx41 1 823 4054 mail: [log in to unmask] --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------