We have seen some annular rings turn black after attempting to solder. At first I thought it was flux residue but after cleaning off the flux, the annular rings are definitely black. Could this be my first case of "black pad"? I always associated it with BGA's. Thanks Peter -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Miguel Vallejo Sent: Wednesday, March 21, 2007 2:21 PM To: [log in to unmask] Subject: Re: [TN] Solderability problems on through holes only. Paymon, Isn't this phosphor starvation what causes "black pad". -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Wednesday, March 21, 2007 2:02 PM To: [log in to unmask] Subject: Re: [TN] Solderability problems on through holes only. Hello Peter, I have not looked at the suspect assemblies. However, this defect can occur when the Nickel under the gold is oxidized prior to the TH component assembly process. The electroless nickel is not pure and it contains 10 to 14 percent phosphorus by weight. The nichel-phosphorus is a good diffusion barrier to avoid corrosion of the solderable surface. If the phosphor content is low i.e. 3 to 5% by weight then the solderable surface will oxidize by each reflow heat application. The oxidize nickel will then prevent soldering to the surface. The link below is a good read on the ENIG surface finish. http://www.pfonline.com/articles/129901.html The assemblies should be reworkable with aggressive water soluble fluxes, some mechanical action and a suitable soldering iron tip temperature. Hope this helps, Paymon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Wong Sent: March 21, 2007 4:18 PM To: [log in to unmask] Subject: [TN] Solderability problems on through holes only. Hi Technetters, We are having a solderability problem confined to only through hole locations where we need some help or advice. We are soldering a no-clean SAC305 alloy to an ENIG finished board. All SMT solder joints (both sides) are fine. During hand soldering in our dedicated lead free area, we are having problems with solder wetting to some of the annular rings and barrels of through hole locations, not all holes. The assembly is an 0.062" thick 4 layer 1"x1" board so it is not thermally challenging. We've built thousands of these in the past without this particular problem. The time lag between smt and through hole assembly is 1-2 days. We've tried using a more aggressive flux such as OA flux with no improvement. The only way that we can get solder to wet is to mechanically scrape the annular rings with a pick. Has anyone seen this before? Why would this only occur on some of the through hole locations and not on smt pads? We have isolated this to a specific lot code of boards and are waiting for some advice from our board vendor as well. Thanks Peter --------------------------------------------------- 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 ----------------------------------------------------- ------------------------------------------------------------------------ ---- ----------- Confidentiality Notice This e-mail and any attachment(s) are intended for the individual or entity to which this email is addressed and may contain information that is confidential. 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Thank you! --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------