The same phenomenon occurs with horizontal HASL. Its normally only associated with mask defined features or tight pad to mask clearances. Re designing the test point and/or mask aperture to provide a high energy point to wet from should solve the problem. We solved the equipment problem by using high velocity solder jets to displace the flux, I am sure a chip wave would work.. -----Original Message----- From: Wenger, George M. [mailto:[log in to unmask]] Sent: Wednesday, August 11, 2004 12:02 PM To: [log in to unmask] Subject: Re: [TN] Solder skipping on ENIG finish Alistair, Are your test pads circular lands or are they vias? What is the thickness of your solder mask? Solder skips in wave soldering on test pads that don't have an opening to the top of the board are not uncommon. Since flux is applied to the board prior to hitting the solder wave, the flux in the well made by the solder mask can prevent the solder from touching the pad. My guess is that the reason you don't find anything wrong with the ENIG pads is because there is nothing wrong with them I assume that you've tried to add solder to the pads after wave soldering and they accept solder so telling you that there isn't a solderability issue. If this is the case than what you are experiencing is a physical soldering issue caused by flux entrapment in a "well". Regards, George George M. Wenger, Andrew Corporation Reliablity / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Alistair Murray Sent: Wednesday, August 11, 2004 3:59 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 ----------------------------------------------------- ---------------------------------------------------------------------------- -------------------- This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. 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