Stu, I have not found a need to add solder paste for BGA replacements of any size and use flux only, typically No Clean. I do prefer to leave an extremely small dome of solder on each pad as part of pad prep to ensure no exposed intermetallic and enhance wetting. We accomplish this under a microscope and perform a 10X visual prior to placement of the new part with a Sniper System (TM). We have had excellent success with the exception of the Altera part with the known warpage problem. Regards, Bruce Misner > ---------- > From: [log in to unmask][SMTP:[log in to unmask]] > Reply To: TechNet E-Mail Forum.;[log in to unmask] > Sent: Tuesday, May 14, 2002 10:34 AM > To: [log in to unmask] > Subject: [TN] BGA replacement > > The M.E.s at my company are struggling with replacing a defective plastic > BGA. > We have an Air Vac BGA machine. The lead M.E. feels that he needs a solder > pad > deposit in place before putting the replacement BGA on the board for > reflow. He > feels that he will compensate for irregular solder balls on the part and > also > possible surface differences on the existing pads which have been wicked > clean > of solder. > > The problem is in putting down the paste. He is teaching a technician to > use a > small medium stiff plastic stencil. The paste is applied with a wide > chisel > blade x-acto knife looking tool. They are getting uneven solder cakes and > icicles between the solder deposits. > > I ask, is that the best way to put down paste? Is it necessary on a > plastic BGA > to put down a paste deposit? Will the stringers pull in when heated or > will they > results in shorts after reflow? > > Any info appreciated. > > Thanks, > > Stu Korringa > Quality Engineer > Smiths Industries Electronic Systems > Grand Rapids, Mi. > > > ********************************************************************** > This e-mail and any files transmitted with it are confidential and may > be legally privileged or otherwise exempt from disclosure under > applicable law. This e-mail and its files are intended solely for > the individual or entity to whom they are addressed and their content > is the property of Smiths Aerospace. If you are not the intended > recipient, please do not read, copy, use or disclose this communication. > If you have received this e-mail in error please notify the e-mail > administrator at [log in to unmask] and then delete this e-mail, its > files and any copies. > > This footnote also confirms that this e-mail message has been scanned > for the presence of known computer viruses. > *********************************************************************** > > -------------------------------------------------------------------------- > ------- > 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 e-mail to [log in to unmask]: > SET Technet NOMAIL > 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 > -------------------------------------------------------------------------- > ------- > --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------