With nitrogen reflow, it will help to reduce the issue. If you use a soft eraser to rub the surface of land pads on the secondary side of the board after the first reflow process, the poor wetting issue will be eliminated/ reduced. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker Sent: Wednesday, 23 September 2009 4:39 AM To: [log in to unmask] Subject: Re: [TN] Imm Sn soldering issue. George Thank you for your interest. Actually I have seen these issues occur on nearly every finish except solder plated boards ( going back to the dark ages). The occurrence has diminished over the years, but it still happens. My guess is it may never be completely resolved as the first reaction is to point fingers at the other guy. Best regards Lee J. L. Parker Ph. D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: Wenger, George M.<mailto:[log in to unmask]> To: TechNet E-Mail Forum<mailto:[log in to unmask]> ; Lee parker<mailto:[log in to unmask]> Sent: Tuesday, September 22, 2009 4:31 PM Subject: RE: [TN] Imm Sn soldering issue. Lee, Okay now that I read you whole response I can see the issues you're talking about and they do have application with both surface finishes. It's just that when you said "you may have problems other than the immersion silver surface" I thought you misread what surface finish Peter asked his question about. Regards, George George M. Wenger Andrew Solutions Senior Principal FMA / Reliability Engineer 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [Office] (732) 309-8964 [Cell] [log in to unmask]<mailto:[log in to unmask]> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker Sent: Tuesday, September 22, 2009 4:25 PM To: [log in to unmask]<mailto:[log in to unmask]> Subject: Re: [TN] Imm Sn soldering issue. George I am aware of that, but my suggests have potential application in either case. Best regards Lee J. L. Parker Ph. D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: Wenger, George M.<mailto:[log in to unmask]<mailto:[log in to unmask]>> To: TechNet E-Mail Forum<mailto:[log in to unmask]<mailto:[log in to unmask]>> ; Lee parker<mailto:[log in to unmask]<mailto:[log in to unmask]>> Sent: Tuesday, September 22, 2009 3:21 PM Subject: RE: [TN] Imm Sn soldering issue. Lee, Peter is having problems with immersion TIN not immersion SILVER Regards, George George M. Wenger Andrew Solutions Senior Principal FMA / Reliability Engineer 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [Office] (732) 309-8964 [Cell] [log in to unmask]<mailto:[log in to unmask]<mailto:george.w [log in to unmask]:[log in to unmask]>> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker Sent: Tuesday, September 22, 2009 3:03 PM To: [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]:T [log in to unmask]>> Subject: Re: [TN] Imm Sn soldering issue. Peter you mentioned that the defects are normally on the second side. I was also wondering if the defects are usually associated with the same features. If so you may have problems other than the immersion silver surface. Issues I have uncovered are soldermask residues and soldering fixtures (if you are using fixtures) that prevent contact of the board and the solder. I suggest that the next time this occurs you process a bare board with no no soldermask or fixturing and see if you get the same result. Quite often I do not. Best regards Lee J. L. Parker Ph. D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: Peter Barton<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask] %3Cmailto:[log in to unmask]>>> To: [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]:T <mailto:[log in to unmask]:[log in to unmask]:[log in to unmask] G%3Cmailto:T> [log in to unmask]<mailto:[log in to unmask]>>> Sent: Tuesday, September 22, 2009 12:33 PM Subject: [TN] Imm Sn soldering issue. Dear Technetters, Hopefully there is someone out there who can help me understand a very specific issue we have using PCB's plated with Imm Sn. namely, non-wetting of solder to some lands on the second side of population after reflow. We have an understanding of this surface finish with respect to the assembly processes. We are careful how we handle the unpopulated PCB's, the PCB's are shipped directly to the line and are only removed from the manufacturer's packaging at the point of use. They are not pre-baked and are subjected to 2 relatively benign reflow cycles. We only ever see the issue on the second side. It occurs on various component types. When it does occur the solder deposited at the printing stage is reflowed and is attached to the component termination, favouring this as more wettable than the PCB land. The problem does not always occur. The assembly is populated in 2 up panels and we have examples where one panel has soldered joints across the piece, whilst the other PCB in the same panel exhibits non wetting in some areas. The assembly has been profiled with a good distribution of thermocouples on a sample assembly to confirm a low delta T and the profile itself is right at the centre of the paste manufacturer's recommendations. We like to have a good process window. I am aware that the 2 possible reasons for this condition are (a) thermal degradation of the finish and (b) possible plating quality issues. We have dismissed excessive thermal input as these have only been subjected to 2 non-RoHS thermal cycles and the PCB's are fresh from the manufacturer. Peak temperatures are only around the 227 deg. C mark. The Sn thickness specification is 0.8 - 1.2 uM. The applied thickness has been measured using XRF as a process control and averages 1.0 uM. I am aware that XRF is only a guide as it cannot segregate out 'available' pure Sn from Sn/Cu intermetallics. We have had an independent lab analysis conducted and example lands where this condition is seen are shown to have very little or no remaining Sn at the surface, the majority being Sn/Cu intermetallics. Other unpopulated plated areas have also been subjected to SEM and EDX for comparison and exhibit what is described as 'islands' of Sn in a sea of Cu/Sn intermetallics. We have not had 'virgin' PCB's analysed yet for comparison as it is costly and we are not sure if we would pick the correct example to look at - it could be a good one. For the PCB experts out there out there I have a couple of questions: 1. If the application of Sn is a displacement reaction with the underlying Cu is there any way that there can be less Sn on some surface areas than others? 2. Are there other reasons that there could be variation in Sn deposits or could lead to the 'islands' of Sn as described by our lab that is seen after thermal processing? 3. Are we missing anything else? Any questions please feel free to ask - this is causing me the biggest headache going. Peter Barton Senior Process Engineer ACW Technology Ltd Dinas Isaf West Tonypandy Mid Glamorgan CF40 1XX Tel: 01443 425275 (direct) Fax 02380 484882 [log in to unmask]<mailto:[log in to unmask]<mailto:E-mail-pb21@wc <mailto:[log in to unmask]:[log in to unmask]:E- mail-pb21@wc> w.co.uk%3Cmailto:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] <mailto:[log in to unmask]:[log in to unmask]:LISTSERV@IPC .ORG%3Cmailt> o:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] <mailto:[log in to unmask]:[log in to unmask]:Listserv@ipc .org%3Cmailt> o:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] <mailto:[log in to unmask]:[log in to unmask]:Listserv@ipc .org%3Cmailt> o:[log in to unmask]>>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives<http:/ <http://listserv.ipc.org/archives%3Chttp://listserv.ipc.org/archives%3Ch ttp:/> /listserv.ipc.org/archives%3Chttp://listserv.ipc.org/archives>> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/cont <http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/con t> <http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/con <http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/con > t> entpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]:sasa <mailto:[log in to unmask]:[log in to unmask]:[log in to unmask] Cmailto:sasa> [log in to unmask]<mailto:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] o:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] o:[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]<mailto:[log in to unmask]<mailto:[log in to unmask] o:[log in to unmask]>>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives<http:/ /listserv.ipc.org/archives%3Chttp://listserv.ipc.org/archives>> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/cont <http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/con t> entpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]:sasa [log in to unmask]>> or 847-615-7100 ext.2815 ----------------------------------------------------- ------------------------------------------------------------------------ ------------------------ This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. 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