Hi Nitin, IPC LF Listservers, <====== A July2005 topic. The link to the topic I am replying to on IPC-LF is: http://listserv.ipc.org/scripts/wa.exe?A2=ind0507&L=leadfree&D=0&T=0&P=20949 <======= We have discussed this before and back a few months ago we briefly discussed a trade press published article from iNEMI by NIST-CarolH on Backwards and Forward Compatibility which partially covers your questions. I would read this as a start. Yours in Engineering, Dave YiEngr, MA/NY DDave -------------------------------------------------------------------------------Leadfee Mail List provided as a service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Leadfree To temporarily stop/(start) delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL/(MAIL) Search previous postings 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 -------------------------------------------------------------------------------