Hi Seppo! I have asked the question in the past, and most of the responses told me that yes, underfilling does help array packages to survive shock, but it is a complicated process that can be difficult, and does have some real drawbacks. One process that you might consider that will help increase shock survivability 3-4 times more than just a soldered array package, is corner bonding. There was a good paper written and presented at APEX last year titled; "Corner Bonding of CSP's; Processing and Reliability" that has a lot of data from drop tests done on corner bonded CSP's to show the increased reliabilty from corner bonding. Granted, the tests done were on CSP packages, but I asked the question if the same reliability gains would be realized with BGA packages and was told that there should be....it's just that the testing was done with CSP's. -Steve Gregory- > Dear All, > > I am doing some checking into the effectiveness of BGA underfill on mobile > handsets. > Typically handset boards have 3-4 BGA's (0.5 to 0.8mm pitch) and have seen > handsets with and without underfill. > PCB thickness is 0.8mm > > Has anyone seen any studies, or have any comments on the reliability of BGA > joints wrt underfill. > Also, any comments on what typically recommended underfill compounds are is > also appreciated. > > Thanks in advance! - and wishing you all a Merry Christmas and a Happy New > Year !. > > -- > Seppo Saario > Voxson Ltd., Core Technologies - Hardware > Design Engineer > Tel +61-7-3268-0745 ; Fax +61-7-3878-1370 > --------------------------------------------------- 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 -----------------------------------------------------