Bill, Our experience in reworking thousands of BGA components indicates that there is a relatively high risk of exposing the intermetallic layer when using solder wick to clear pads of old solder prior to placing new components. Perhaps the small size of the pads relative to the mass of the wick and soldering iron make them venerable to the exposure of the intermetallic during the wicking operation. Our basic instruction to technicians is not to remove solder from the old pads so that the pads look, crusty or granular. Leave a sheen or a slight layer of solder to protect from intermetallic exposure. A skilled and experienced 'prep' technician can eliminate this problem. However, big smoking irons or ultra-light efficient irons can create problems when wick is ground into the site in an effort to get every last bit of solder off the pads as quickly as possible. More and more people use a teflon tipped vacuum removal device to evacuate solder. This prevents intermetallic exposure and limits collateral damage to solder mask in the area. Jeff Ferry CEO Circuit Technology Center, Inc. On Tue, 23 Oct 2001 14:18:38 -0400, Bill Raymond <[log in to unmask]> wrote: Hello all, During the process of replacing PBGA devices, we use solder wick to remove excess solder from the board pads before stencil printing (with a mini-stencil) solder paste and then using our Air-Vac system to place and reflow the BGA. My question... what risk do we have in exposing the intermetallic layer while we are cleaning off excess solder from the board pads with solder wick? Every once in awhile, we see a solder joint that just seems not to wet to the board pad... it's as if the solder paste that was printed on that pad "jumped" up to increase the size of the BGA solder ball and just didn't wet to the board pad. So now that larger looking ball is simply resting on the pad. I am using a small mirror ( .250 inch square) mounted on a dental pick (for a handle) and a stereo microscope... to inspect the outer row of BGA balls. > >Thanks, Bill > >--------------------------------------------------------------------------- ------ >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 ---------------------------------------------------------------------------------