Alex, Unlike a QFP or CCGA, a BGA with eutectic balls floats on top of the solder. This mean there is no such thing as a maximum weight for self centering. There is however, a maximum weight before you squash the balls into each other, causing shorting. (I don't know what it is, but Daan might.) For bottom side reflow, I have heard John Thorup and Phil Zarrow claim that the grams per square inch of pad mating area should be less than 30. Hope this helps Ryan Grant Advanced Technology Engineer MCMS (208) 898-1145 [log in to unmask] > -----Original Message----- > From: Alex L Chan [SMTP:[log in to unmask]] > Sent: Thursday, October 12, 2000 2:22 PM > To: [log in to unmask] > Subject: [TN] Question about max. g/ball for BGA self center > > Hi Technetters, > > Do anyone have a quick answer about what is the maximum weight in term > of g/ball for BGA self center? Which means that if the component is > over this limit it will not self center. Also for double sized reflow, > what is the maximum g/ball that the BGA component will fall off? > Assuming 1.27 mm pitch and using 0.75 mm eutectic balls. > > Thanks, > Alex > > -------------------------------------------------------------------------- > ------- > 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 > 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 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 ---------------------------------------------------------------------------------