Nee hao GA Tan, The Tg of the underfill is not much of a concern; the critical properties are the CTE over the application T-range and the modulus of elasticity. It has also been shown by work done at Motorola that slow curing underfills [at least some] do not give much reliability improvement at low failure probabilies [that is the failure distributions become very wide]; whereas snap-cure underfills produce tight failure distributions. You might want to take a look at my reliability column: Engelmaier, W., “ Reliability Improvement with Underfill,” Global SMT & Packaging, Vol. 6, No. 3, March 2006, pp. 66-67. Regards, Werner Engelmaier 可靠性先生 Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com ************** Play online games for FREE at Games.com! All of your favorites, no registration required and great graphics check it out! (http://pr.atwola.com/promoclk/100000075x1211202682x1200689022/aol?redir= http://www.games.com?ncid=emlcntusgame00000001) --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------