Hi Phil, my first thought reading your discription was also " hey, there´s different thermal mass with these microvias, so it needs a different profile ". It´s the most obvious difference and I would look at that first. Wolfgang -----Ursprüngliche Nachricht----- Von: Werner Engelmaier [mailto:[log in to unmask]] Gesendet am: Mittwoch, 30. Mai 2001 01:48 An: [log in to unmask] Betreff: Re: [TN] Pad in Via for BGA's - Part II Hi Phil, I think your pads/solder balls with vias run somewhat cooler than those w/o vias for the same machine reflow profile, i. e., the actual reflow profile for these pads/solder balls with vias is lower. this is because the via copper structure and connected copper traces act like a heat sink. Normally the PCB runs hotter the the components, however, because the BGAs shield the PCB from both convection and radiation, the PCB portion underneath BGAs is cooler. I would recommend running actual profiles at these locations if you need convincing. It is likely that your profile does not have much excess peak temperature, thus the affected solder balls are not liquid long enough at a high enough temperature for low viscosity to let the bubbles move fully up. Remember, solder does get pasty at its Liquidus not Solidus temperature. Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 904-437-8747, Fax: 904-437-8737 E-mail: [log in to unmask], Website: www.engelmaier.com ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------------