Hi Peter, When you say that you had the PCB analyzed for contamination, by what method? As I mentioned to Alistar, the analyst looking for a thin layer of nickel oxide on the surface of a thin layer of gold must be very careful in the techniques employed to "see" this oxide layer. It is very easy to miss, I have seen it over-looked quite a few times by expert analysts. I have seen conditions where the ENIG surface would not wet in random areas of the PCB, and when we performed the analysis we found nickel oxide (in some cases a very thick nickel oxide layer) present. I would be happy to talk with you offline if you would like more information. Wade McFaddin Nextek Inc. 256-772-1995 ext.1064 -----Original Message----- From: Peter Barton [mailto:[log in to unmask]] Sent: Friday, August 13, 2004 7:48 AM To: [log in to unmask] Subject: Re: [TN] Solder skipping on ENIG finish I have a supplementary question relating to this answer. Could a low amount of gold in ENIG also be attributed with poor solderability of assemblies at second side reflow? We have an assembly that is ENIG finished, and solders perfectly well on side 1. When turned over to second side, placed and reflowed, a lot the joints are not wetted to the pads. There is sufficient solder, and the components themselves have wetted. If the process is reversed i.e. side 2 reflowed first, followed by side 1 then there is non wetting on that side. Could it be that if the immersion Au is particularly thin that the first side heating process could promote oxidation of the underlying Ni and this oxidation migrate through the thin Au? I have had the PCB analysed and no contamination can be found. Regards, Peter Barton ===== Original Message from [log in to unmask] (TechNet E-Mail Forum) at 12/08/04 09:15 >Alistair > >The presence of Nickel oxide on suspect pads shows up the problem. There >is a lot of material on the NET/ archives and lots of gurus out there >who advise higher gold in ENIG to cure this problem. The problem occurs >due to low Gold in ENIG. U can ask for 0.1microns minimum. > >Best wishes >Anil > > > > >-----Original Message----- >From: Alistair Murray [mailto:[log in to unmask]] >Sent: Wednesday, August 11, 2004 1:29 PM >Subject: Solder skipping on ENIG finish > >Hi to all. This is my first visit to this forum and I apologise if this >subject has been aired and exhausted in previous correspondence. > >My customer has an issue with a simple double sided PTH board (no >surface >mount pads) with ENIG finish all over. After standard wave soldering, he >is >experience random skipping of test pads on the solder side. Normally, >this >would not be a problem but some of these test pads do not provide a good >electrical contact when subjected to electronic testing. Again, this >phenomenon is quite random. >The wave soldering parameters have been modified but with little success >as >the skipping persists in a random fashion. >We have carried out SEM analysis on good and suspect pads and have >concluded >that (1) there are no unexpected elements present thereby eliminating >contamination such as solder resist (2) evidence of nickel oxide is >present >on the suspect pads (3) there is a physical difference in the material >structure of the good and suspect pads - the good test pad has an >homogenous >structure with no discontinuities whilst the suspect pad is not >homogenous >and has a series of parallel lines which are boundaries in the material >deposition (4) SEM analysis on the test pin found no insulating >material. > >Can anyone explain how such skipping can occur and how it can be >prevented? >The random failure to make electrical contact on non soldered pads is >puzzling. We are convinced that there are no insulating elements >present. >Could the different structures be a clue? Could the deposition rate >differ >from pad to pad? Could the process control parameters of the nickel and >gold >solutions be a factor here? > >Thank you for your anticipated help. > >Alistair F Murray >Technical Manager >Artetch Circuits Limited >Tel: 01903 725365 >Voice Mail Ext. 1260 >e-mail: [log in to unmask] >www.artetch.co.uk > >--------------------------------------------------- >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 847-509-9700 >ext.5315 >----------------------------------------------------- > >--------------------------------------------------- >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 847-509-9700 ext.5315 >----------------------------------------------------- ----------------------------------------------------------------------- Peter Barton Senior Process Eng ACW Technology Ltd Dinas Isaf West Tonypandy Mid Glamorgan. CF40 1XX Wales Tel: 01443 425200 Fax: 023 8048 4882 International Tel : +44 1443 425200 International Fax : +44 23 8048 4882 Website/URL: www.acw.co.uk --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------