Cheryl's point on 2ndary reflow is a good one. I"ve seen this a couple of times. Also, the fix of changing the wave solder parameters is good too. Another idea for corrective action, if changing the wave parameters is not a good choice is to add a thermal barrier to the area under the QFP on the bottom side of the PCB. Polyimide tape (Kapton) works good for this. A longer term fix may also be to mask over the vias in that area under the QFP. The mask can provide enough of a thermal barrier to prevent 2ndary reflow. Kelly On Thu, 6 Jan 2005 12:27:31 -0600, Cheryl Tulkoff <[log in to unmask]> wrote: >Roger - > >Does this board go through the wave solder process after SMT? You could be >seeing secondary reflow of the SMT joint at the wave. This happens when the >temperature of the wave process is sufficient to remelt topside joints. It >usually happens only on fine pitch QFPs(smaller joints with less solder >volume). To avoid this, most people will run the wave solder temperature >lower (240-250 C rather than 260C) and the conveyor faster (5.5 ft/min or >higher). > >I can send more info if you're interested in checking it out. > >Thanks, > >Cheryl Tulkoff >Phone:(512) 683-8586 >Fax: (512) 683-8847 >National Instruments >11500 N. Mopac Expressway >Building A >Austin, TX 78759-3504 > > > > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------