Hi Alistair, You mentioned that you had SEM analysis performed on the pad surfaces and did not see any evidence of nickel oxide. Be sure that the analyst is using low voltage SEM/EDS (5 keV or lower) when performing the analysis or you may never see the presence of an oxide layer. We have seen this quite a few times, and when the analysis is performed at the more standard SEM/EDS conditions of 20 keV or higher the electron beam penetrates the surface layer and it is missed. I would be glad to talk to you off-line about the technique if you are interested. Thanks and good luck, Wade McFaddin Nextek Inc. -----Original Message----- From: Alistair Murray [mailto:[log in to unmask]] Sent: Wednesday, August 11, 2004 2:59 AM To: [log in to unmask] Subject: [TN] 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 -----------------------------------------------------