Parvez, You're absolutely right. Re-flow parameters are certainly critical, especially with sensitive paste. As I mentioned (not very well), improper re-flow profile parameters can dry out the flux, or worse, burn it. Recently, at SMTA, Charles Bradshaw presented an interesting paper titled "Thermogravimetric Analysis Predictions of Reflow Profile of Solder Pastes" that is basically a scientific method of determining the reflow profile for any specific flux vehicle. That paper goes into better specifics as to what will happen to the flux for incorrect reflow profiles. In addition, I neglected to mention that voids in BGA's happen only when paste is used. If only flux is used, the tip of the ball can begin wetting the pad from the inside out to the edge of the pad, thus driving the flux in front of the molten solder. Thanks Ryan Grant Process Development Engineer MCMS (208) 898-1145 FAX (208) 898-2789 [log in to unmask] >-----Original Message----- >From: Parvez M.S. Patel [SMTP:[log in to unmask]] >Sent: Monday, September 27, 1999 6:58 AM >To: [log in to unmask] >Subject: Re: [TN] BGA voids > >Ryan >that was really good reply. >Dont u think reflow profile parameters are also critical? > > > >-- >PARVEZ M.S. PATEL ADDRESS: >GRADUATE STUDENT, APT.#2, 182 Westend Avenue, >SYSTEMS SCIENCE AND INDUSTRIAL ENGG. BINGHAMTON, NY-13905 >STATE UNIVERSITY OF NEW YORK, NEW YORK. U.S.A. >BINGHAMTON-NY. > >PH:607-770-7507 > >EMAIL:[log in to unmask] > [log in to unmask] > >URL:bingweb.binghamton.edu/~bg22842 > >############################################################## >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 ##############################################################