Alex, The spacing of BGA balls after reflow will vary significantly this will be due to how the balls collapse and the co planarity of the BGA site. Another words some joints may form columns if there are co planarity issues and on the flip side some of the balls will collapse more than desired due to co planarity. Minimum spacing is very difficult to gauge because of this. Generally BGA's are not used in high voltage aplications (as far as I know) so.... If the ball are not shorted together than you have done your job. There should be no problems with different potentials jumping around Good luck. Best regards, Shawn C. Murphy Process Engineer 6640 185th Ave NE Redmond, WA 98052-5038 [log in to unmask] Tel: (425) 885-0107 Ext. 678 Fax: (425)867-5600 -----Original Message----- From: Alex L Chan [mailto:[log in to unmask]] Sent: Tuesday, April 17, 2001 5:32 AM To: [log in to unmask] Subject: Re: [TN] Minimum spacing between two BGA solder joints? Hi Steve, Sorry if I didn't present the question clearly. The question I am asking is refer to the spacing (gap) between two solder joints not the pitch of a BGA component. For example, in a 1.27mm (50 mil) pitch BGA, a solder joint is roughly 35 mil after reflow, that leave the theoretical spacing between the solder joints become 15 mil. However for some reason the package that used may have balls that off the true position which may result the two solder joints come very close together after reflow. What would be the minimum allowable spacing between the two joints? Thanks, Alex "Stephen R. Gregory" wrote: > Hi Alex! > > Do you really mean .005"? Sounds pretty 'friggen tight to me. Here's a page > that talks about ball pitch on uBga packages and chip scale packages: > > http://www.ednmag.com/ednmag/reg/1995/052595/11df1.htm > > No where are they getting that tight...I just want to say, I see you're from > Alcatel, so you're in the packaging business, have a heart on us assembly > guys, you may design a package that works, but then leave it up to > "floor-rats" like us to figure out how to put these things together. A BGA > package that goes down to .005" spacing is asking too friggen' much!!! I > don't think I'm alone in that observation....I could be wrong...(it hasn't > been the first time) > > Geeze, you designers need to get down on the manufacturing floor...don't mean > that badly, just a necessary requirement before you push the limits... > > -Steve Gregory- > > << Hi, > > Do anyone have any literature referring to what is the minimum spacing > between two BGA solder joints? From talking to many people, 0.005" seem > > to be the most commonly use number. Do people agree with this number? > Why? > > 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 > 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------