Back in the mid-90's while at Motorola, we conducted a cursory evaluation of PbSn flip chip assembly using square pads vs. round and contrary to initial expectation, the square pads showed greater temp cycles to failure. Without a large amount of study this appeared to be the consequence of the large contact interface area with a square of dimension 'x', vs a round pad with diameter 'x'. This may or may not be relevant to the PbFree discussion. Regards, 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: Brian J. Toleno, Ph.D. [mailto:[log in to unmask]] Sent: Wednesday, March 24, 2004 1:12 PM To: [log in to unmask] Subject: Re: [TN] FW: Round SMT pads It is not an issue of reliability (to my knowledge that hasn't been tested, but I don't see how it would be a major impact as long as you have good fillets on the leads). This is more of an appearance issue. This is especially true with OSP pads where the exposed copper may eventually green. Brian J. Toleno, Ph.D. Sr. Applications Chemist Loctite Electronics 15051 East Don Julian Rd Industry, CA 91746 Ph: 626-968-6511 x304 Cell: 626-215-0879 ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. http://www.loctite.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 847-509-9700 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 -----------------------------------------------------