Hi Steve, I have not seen this on J leads but definitely under bga.s. I measured up to 200C under a topside bga* when it went over the wave, so I reduced the preheat (it was too hot anyway) and used peelable solder mask under the bga vias. This did the trick but was time consuming. I was fortunate that I was able to convert the process flow to double side reflow with pin in hole. Hope this helps. Regards Eric Dawson * An image has just formed in my mind of a bottom side bga going over a wave. I think I need to lie down in a darkened room. > -----Original Message----- > From: [log in to unmask] [SMTP:[log in to unmask]] > Sent: Tuesday, April 23, 2002 2:07 AM > To: [log in to unmask] > Subject: [TN] Secondary reflow over wave... > > Hi All! > > Got a situation here that I think is secondary reflow... > > Have a board here that has some J-leaded DRAM that in functional test, > they > can get the board to pass test by putting some pressure on top of some of > the > 40-pin J-leaded DRAM's that are causing them to fail... > > Out of SMT things look fine, but I have observed some boards that have > failed, show an unusual solder joint appearance after wave. The board is > "swiss-cheesed" with vias, and none of them are tented. Every pad has a > via, > they alternate, some have .050" traces to the pad, some have .020" traces > to > the pad. > > Where we're seeing problems is where there is a bank of them (like a grid > of > 2 by 8 of them layed-out side by side). > > I'm thinking secondary reflow because of the open vias...or could be CTE > mis-match between the part and the board. It's a .062" FR4 board, with > fairly > large 40-pin SOJ's, could be experiencing some hellacious mismatch, no? > The > gull-wing parts we don't see the problem, even though the via placement is > the same standard as with the J-leaded parts...J-leads aren't as > compliant? > > Gonna hook-up the mole tomorrow, attaching it to one of the J-leaded parts > to > learn what it is seeing...will tell me a lot... > > Just wondering if anybody else has run into this before... > > -Steve Gregory- > > -------------------------------------------------------------------------- > ------- > 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 ---------------------------------------------------------------------------------