Dear All, We're looking at using an LGA interconnect for one of our products. It will be a module, pre-manufactured on a FR4 or FR5 substrate (~1mm thick) up to 40mm x 40mm in size and weighing approximately 10g. The intention is for the OEM customer to SMT this module onto their application board which is also FR4/prepreg based board. We are considering about ~200 pads, with a square pad size of 0.8mm x 0.8mm. The soldering is NSMD defined. The paste mask we're looking at is 0.6mm^2 to 0.7mm^2. The pitch of the pads is 1.4mm in both axes. Would anyone here know of any design guideline docs (IPC?), and/or studies done on the reliability/manufacturing of LGA based interconnects?. Some areas that we're concerned with include: 1. Thermal expansion/stress with possibly different PCB substrates across 40mm. (relatively large).. - Are CGA's any better in this regard?, can CGA's come in very low profile (<0.3mm?) 2. Reliability with application board flex/twist and cracking of pads?, Possible board warpage problems? 3. Resistance to shock? - has anyone used underfill for LGA's?. 4. SMT machine placement accuracy? - Would anyone have any comments on any expected problems with the placement accuracy of larger "parts", our module would be up to 40mm x 40mm and SMT'd? Any comments or suggestions would be very much appreciated, wishing you all a Merry Christmas and the best in 2003!. Seppo. --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------