Hello folks Long time no posting, been kinda busy with some exciting new business developments - more of which later - and Ingemar forced a reaction: Given that my company name is Concoat, your heading and some of the comments make me shudder - maybe its an earthquake in merry olde England? Like Ingemar, I too learnt quite a lot from this issue, especially Brian Ellis' comments regarding silicones. That was a curious one. I should have thought, but then what do I know, that a soft "squooshy" material like certain silicones (maybe that should be Silly-Cones?) would only react in a "rigid" sense when subjected to kinetic energy impacts rather than the more insidious thermal creeps!? Anyhow, I am not entirely sure whether an underfill or a coating can - should - ought to be used under BGA's. The issue I guess, is maintaining the integrity of the solder joints, and maybe, just maybe, the current soldering methodology is the weak link for these devices? Our new condensation soldering technique - that's vapor phase to the older techies - certainly provides for a uniform and effective soldering of such devices. The use of a conformal coating or an underfill. Depends on the nature of the coating and perhaps more importantly, how it is cured to avoid residual solvent entrapment and the like. Obviously "squooshyness" is an important factor - maybe there is scope here for more thermal dynamic work on encapsulants, underfills and coatings - anyone for tennis? Regards, Graham Naisbitt [log in to unmask] www.concoat.co.uk Concoat Limited www.concoat.co.uk <http://www.concoat.co.uk> Alasan House, Albany Park CAMBERLEY GU16 7PH UK Phone: +44 (0)1276 691100 Fax: +44 (0)1276 691227 Mobile: +44 (0)79 6858 2121 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Ingemar Hernefjord (EMW) Sent: Monday, February 26, 2001 02:52 To: [log in to unmask] Subject: [TN] pumping concoat Hi all, I have triggered some BGA soldering issues last weeks and got superb responding! We have learnt a lot!. Among answers one warning not using concoat under very large BGAs, could cause pumping effects. Guess Tech-Shot could answer as well, but more gurus at TechNet. Graham N, he must at least have a refresher for me. Got this b4: 1. try skip concoat, best living for BGA solderings 2. if using concoat, always underfill 100% first 3. if using concoat and no underfill first, you'll get closed in gas and contaminations and CTE mismatch >disasters So, my question is: is 3 above reality for some of you? Don't your balls like such pumping? Thx in advance Ingemar Hernefjord Ericsson Microwave Systems ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------