Could it be a typical 'black pad' issue with ENIG? Hand soldering might introduce local warpage of the board, which could open up weak joints. A 'dye and pry' test should tell you the location of the failed pads, and the correlation with the location of hand soldering. Liang Yin Process Research Engineer Unovis Solutions > Date: Tue, 22 Jul 2008 07:44:00 -0500 > From: [log in to unmask] > Subject: [TN] They solder well... But they don't work! > To: [log in to unmask] > > Here's a good one for the collective 'mind-meld'... > > We have a two-sided, non-RoHS compliant, all-SMT assembly (no PTH parts) > that is reflowed under a leaded profile (cooler reflow temperatures than > Pb-free). There is one 44-pin QFP on the topside of the board that > consistently solders well (i.e. passes all IPC-A-610 Class 2 inspection > criteria), but fails test until it is reflowed with a hand iron, a little > flux and wire solder. We have about a 25% pass rate without reflowing the > QFP. That jumps to around 95% once the QFP is reflowed. Several different > date codes of the device have been tried with similar results. > > Thinking the ENIG pads under the device leads might be contaminated, we > cleaned them on several test case 4-up panels, with no change in yield. > Thinking it might be contaminated leads on the devices, our process guys > gently scraped off the tinned coating on the leads of several devices and > took it down to the Beryllium Copper finish. Same resultant yield. > > We've re-run the failing assemblies through a higher reflow temperature with > extra 'tacky flux' on them, trying to get a better reflow and use the action > of the flux to purge any contamination that might be interfering in the > solder junction. When done, the solder junctions on the device look like a > 'Target - Class 1,2,3' picture from IPC-A-610, but the yield is still around > 25% unless we reflow the junctions with an iron, some flux and wire solder. > > There may be some things we're overlooking, but it's coming down to where we > believe the wire bonds to the lead frame material could be the source of the > problem. The intense, direct heat of the soldering iron might be enough to > generate a reflow of the wire bond, resolving any bonding issues. But, on > several different date codes? I will be getting the vendor involved shortly > to test the devices and see if they come up with something. I'm fairly > skeptical about doing this as typically the normal answer I get is 'all is > working as designed'. > > We are all scratching our heads on this one... Any 'words from the wise' > would be appreciated! > > Thanks! > Dale Ritzen, CQA > Quality Manager/ISO Management Representative > Austin Manufacturing Services > Email: [log in to unmask] > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 > ----------------------------------------------------- _________________________________________________________________ Keep your kids safer online with Windows Live Family Safety. http://www.windowslive.com/family_safety/overview.html?ocid=TXT_TAGLM_WL_family_safety_072008 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------