Jerry ; this task is quite possible using reflows with bottom temp chilling ; up to some 30'C differentiation can be achieved ; therefore keeping you below liquidus on second pass on bottom side . Sorry to disappoint you , however if you do not have reflow rigged with chiller you still have a pretty good excuse . Paul Klasek http://www.resmed.com > ---------- > From: Jerry Cupples[SMTP:[log in to unmask]] > Sent: Wednesday, 24 June 1998 8:15 > To: [log in to unmask] > Subject: [TN] ASSY: BGA sanity check > > Hello, TechNet.... > > Soldering (inline convection furnace) BGA's on both sides of a board > is > beyond my own experience, but it seems to violate a principle (at > least an > imaginary one) related to the controlled collapse, or perhaps liquids > under > tension. > > For a board design using 3 commercial BGA packages (PBGA 256, eutectic > balls on 1.27 mm pitch), am I obstinately blocking the path of > progress by > requesting that this package style be confined to only one surface of > a new > board design? > > If you are doing this today and it is a piece of cake, go ahead and > brag; > but I would prefer to hear that caution is well advised, i.e. tales of > misery, shame and corporate disaster resulting from such mistakes. ;-) > > > cheers, > > > > > Jerry Cupples > Interphase Corporation > Dallas, TX USA > http://www.iphase.com > > ################################################################ > TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for > additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ > ################################################################ TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################