I appreciate all of your comments on the history of Au embrittlement versus the supposed lack of the same history for Ag embrittlement, etc. However, lets take the facts for what we have here with this particular case (Steve's boards). The question is whether soldering a gold-over-alloy-42 component termination (the component lead) to a circuit board with IAg finish using tin/lead solder (right?) could have resulted in a type of alloy where the combination of the gold and silver, and the slower dissolution rate of the nickel, and the fact that the particular components that failed are known to get hot enough to burn your finger could have led to a brittle fracture failure. It may not have been any single one of these variables, but a combination of all of them. I could not find out in all of the emails if the solder was 63/37 or SAC. If it was SAC305, than factor in a much more brittle alloy with another, additional, small amount of silver. 1. I believe that there is quite a bit of evidence related to the gold embrittlement issues, I hope we all agree on that. 2. We all know there are issues with silver migration/nucleation. There are good papers on that, beginning with Kirkendall's, and many since. 3. We all know the issues with soldering to alloy 42. 4. We know the alloy 42 leadframe is not compliant. 5. We know that the component is getting very hot, probably expanding at a much faster rate than the circuit board underneath it during initial powerup. So there is probably a pretty good CTE delta to deal with. Therefore the question is, can a combination of noble metals cause some similar embrittlement issues, compounded by having to form the IMF with the nickel. And is this, in turn, exacerbated by the fact that there are certain compliance issues with the component leadframe? And the fact that in this particular design, the components get very hot. Does this not sound like a recipe for disaster? Sure it does. Steve's hunch about the heat and the fact that the leads are gold and the board is silver rings very true. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Friday, May 25, 2007 1:50 PM To: [log in to unmask] Subject: Re: [TN] Silver Embrittlement? Were the issues with silver plated component issues back i Dave, Were the issues with silver plated component issues back in the SMART conference era diagnosed as solder joint embrittlement by silver because of too thick a plating or were they termination failures on the silver plated components. In the RF world silver plating is liked by the design community because of its electrical properties. However, solder assembly engineers always have difficulty trying to make reliable solder joints to components that have upwards of 15 to 20 microns of silver plating. When you look at the dissolution rate of silver into solder you realize very quickly that when you try to solder to silver plating this thick you wind up making a solder joint to the plating and not to the base metal. So the question really is that when a solder joint made to thick silver fails why did it fail? Was it due to silver embrittlement or was it because you made a solder joint to silver rather than a base metal. If all of the silver isn't dissolved then if you evaluate the silver content across the termination interface you see that the silver content in the solder may be a couple of percent but when you reach the silver plating side of the termination the silver content is at 100%. One needs to make sure that an analysis of the failure mode is done in order to classify solder joint failures. I for one do not believe that silver embrittlement is worst than gold embrittlement. Certainly I've seen many more solder interconnection failures on joints made to thick silver plating than I have to ENIG or even thick 1 micron of gold plating but I've never seen any data anywhere that shows solder joints made to silver those thickness is 0.05 to 1 micron is any more brittle that solder joints made to 0.05 to 1 micron of gold. Regards, George George M. Wenger Andrew Corporation Wireless Network Solutions Senior Principal FMA / Reliability Engineer 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [Office] (732) 309-8964 [Cell] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, May 25, 2007 12:51 PM To: [log in to unmask] Subject: Re: [TN] Silver Embrittlement? Hi folks! Just a comment. Some of Werner's comments of Ag embrittlement are based on some ceramic components with silver plated finishes which resulted in severe solder joint issues on a series of investigations back in the SMART conference era. The IPC-4553 Immersion Ag finish group is in the final stages of finishing up an investigation where Immersion Ag surface finish was applied to test vehicles in both 1X and 3X thicknesses plus combine with SnPb and Pbfree soldering processes. The goal of the testing is to characterizes and determine if silver embrittlement of solder joint can be created under practical applications. The thermal cycle testing is complete and 100+ cross sections are undergoing SEM elemental mapping analysis. The report will be completed this year - keep an eye on the IPC-4553 group activities. Dave Hillman Rockwell Collins [log in to unmask] Werner Engelmaier <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 05/25/2007 08:12 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: [TN] Silver Embrittlement? Hi Lee, Au- and Ag-embrittlements are certainly documented?the combined effect is simply my extension of the phenomena. 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