In a message dated 11/16/05 15:21:55, [log in to unmask] writes: > Couple questions regarding the dreaded lead free process. > 1. Do I need to request a different process for PCB fabs, what is > the difference if any? > A: It depends. For thin PCBs with components of near-uniform size you may be o.k. For thicker PCBs and components with significant differences in thermal mass you need to specify: hi-Tg/hi-Td/low CTE materials [beware of datasheets--lots of wrong info on them] [ you may want to specify STII=>215], you need to specify E3 copper foil for internal layers, you need to specify at least 1.2 mils of Cu in the through-holes, you need to specify vigorous moisture bakeout prior to soldering process. > > 2. I understand that lead free components require a higher > temperature and longer reflow time, which may affect other component > reliability. Not all the components we use are available for lead free > processes. Any recommendations on the processes to be used with a > mixture of leaded vs. lead free? Is this wise? What should we be looking > out for? > A: iNEMI has determined that for components the MSL rating drops one level for every 10C increase in soldering temperature > > 3. I did not want to recreate the wheel, anyone have a test plan > or qualification plan available to qualify this type of process? > A: Look at IPC-9701A at least for a partial answer. > > 4. And any recommendations on a lead free process class that we could > send a few of our technicians to? > A: Technicians you might send them to some of Bob Willis' courses; Engineers and Designers you might send to my workshops [next ones in Boston December 5 and 6]. Regards, Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com --------------------------------------------------- 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 847-615-7100 ext.2815 -----------------------------------------------------