The ability for water to diffuse out of the package is a key factor. Generally speaking the thinner packages have greater moisture stress resistance (MSL), if all other factors are the same. Here the packages you present have mixed variables. I believe that the possible, small, negative MSL impact that may occur going from 44 to 64 leads is much less than the likely, strong, positive MSL impact expected going from a 4.5mm thick package to a 1mm package. Numerous other factors are important (size of leadframe die attach pad, size/thickness of die, Ag on the die attach pad, leadframe thickness, choice of mold compound, etc. Best regards, Leo Leo M. Higgins III, Ph.D. Director of Applications Engineering ASAT, Inc. 3755 Capital of Texas Highway, Suite 100 Austin, TX 78704 ph. 512-383-4593 fax. 512-383-1504 -----Original Message----- From: Genny Gibbard [mailto:[log in to unmask]] Sent: Friday, October 08, 2004 1:20 PM To: [log in to unmask] Subject: [TN] Moisture sensitivity Just a question for interest sake. Are there any general correlations between package size, and lead numbers, and moisture sensitivity that can be made? For instance, do you think a 17.5mm square 44 lead 4.5mm thick package would have less or more moisture sensitivity than a 16mm square 64 lead 1 mm thick package. The IC's have different functions. Gut feeling, I think the 64 lead would have more sensitivity. It is smaller, with more and finer pitch outside connections. As dimensions get smaller, I think the danger of moisture doing damage goes up. Also, since there are more leads I feel that there are more locations that possibly moisture could get in, as the potential for seal breaks is probably greater at interfaces between plastic and metal? Am I out to lunch in my general reasoning? Just thought I would spice up Friday. To all those Canadians out there, enjoy your turkey and pumpkin pie this weekend. Genny Gibbard (mailto:[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 -----------------------------------------------------