Z axis expansion may weaken or break the plated through holes. > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of > [log in to unmask] > Sent: Friday, August 08, 2003 8:47 AM > To: [log in to unmask] > Subject: [TN] Wave Solder Preheat > > > Hello Technetters, > > I have a family of boards that to achieve 100% hole fill (I'm > building to IPC-A-610C class 2 - yeah, I know 100% isn't > required), I need to preheat the topside of the board to > approximately 310F at about 1.75 ft/min (maybe a 6-7 second > dwell). I usually follow the 180-220F rule-of-thumb, so I'm > asking: What are the potential or real problems? Also, the > flux is OA. > > The family of boards are .050-.070" made out of either FR4, > GE TEK, or NELCO 4000-13. They are also waved in a selective > soldering pallet with an aluminum plate on the topside over > 90% of the components to hold them in place per a design > specification. > > Will I damage the board or components (with immediate > noticeable failures or latent field failures)? Or is the > 180-220F guideline more from the old WS6536/Mil-Std-2000 days > and todays fluxes, boards, and components can handle the temperatures? > > Thanks in advance for the help, > > Al Kreplick > Sr. Mfg. Eng. > Teradyne, Inc. > --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------