Bob, I assume you are working with CBGA? what sort of stand off, package size etc are you looking at, is it fully populated, or is there a "naked zone" by the die edge (always liked that phrase, don't know where it came from, don't hear it often but it brings a smile to my face every time) sorry, are you cleaning before underfill or using one of them funky flip chip no clean chemistry type affairs? During discussions in RL, I was told (so take this with a pinch of salt) that when selecting an underfill the cure schedule is of critical importance, if its a high temp fast cure, you run the risk of creating a material that is quite rigid at operating temps, which can actually decrease solder ball life, similarly, if you use to low a cure, the epoxy is too soft to do any good, and when it hits Tg it expands like mad, and can still reduce life. I gather that these are less of an issue with flip chip and CSP etc as they are so damn small, but with BGA the large amounts of material make it an issue. I guess if you're working with PBGA it could be even worse due to the flexibility of BT compared to a ceramic inetrposer? Also, isn't this expensive? Regards, Roger Roger Massey Materials Technologist Motorola AIEG UK -----Original Message----- From: Bob Vanech [mailto:[log in to unmask]] Sent: 26 October 1999 07:20 To: [log in to unmask] Subject: [TN] BGA Under-fill To Jeff, John, HGross, Kelly, Vidya, ETC. Quick thank you for your vendor information. Still need any BGA under-fill guidance that is out there in TN land of the assemblers. How about it Kelly? I would think that you might have some experience in BGA under-fill, or was it too painfull to remember and you've blocked it out of your memory?.. ;-> Any war stories would be appreciated. Have a great Tues. Regards, Bob Vanech Bob BVAN Enterprise ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################