Thank you George, I completly agree with you. I probably should have been more specific talking about the BP and brittle fracture. :-) what I meant is that if a component can be almost blown off the board, then I wouldn't call it a case of fracture at all. I referred to Ni-p later just because many thinks that the layer is involved somehow, but again only for ENIG!!! It puzzles me why it happens with electrolytic plating, but it's a different story all together. Have a nice weekend (whatever of it you have left). :-) Vladimir Sent from my Blackberry Wireless Vladimir Igoshev, 519-888-7465 ext.5283 -----Original Message----- From: TechNet <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Sent: Sat Apr 16 13:29:05 2005 Subject: Re: [TN] ENIG Gold Embrittlement Vladimir, No need to be sorry. You can intervene anytime because I respect your opinion and observations. I'm certainly not well versed in fracture mechanics and have never had enough time to do a through study of "Black Pad" failure. My view of brittle fractures is simplistic. I view a brittle fracture as a rapid run of a crack or cracks through a stressed material that leaves a relatively flat surface that exhibits very little if any sign of plastic deformation. Given this view, you can tell why I thing the "Black Pad" and "Gold Embrittlement" failure signature look like brittle fractures. Secondly, I don't think in my response to Don that I indicated that the gold embrittlement fracture path goes along the intermetallic/Ni-P interface. We've seen "gold embrittlement" brittle fractures on solder joints to both ENIG and electrolytic plated NiAu, who's Ni contains no P, surface finishes. The majority of brittle fractures we've seen appear to be intergannular in that they occur along grain boundaries and once in a while we'll see transgrannular fractures (i.e., fractures through grains). Actually, on many of the brittle fractures we've analyzed we have seen fractures between the Au-Sn intermetallic and bulk solder, between the Au-Sn intermetallic and adjacent Ni-Sn intermetallic, between the Au-Sn intermetallic and plated Ni, as well as through the Au-Sn intermetallic. Regards, George George M. Wenger, Andrew Corporation Reliability / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: Vladimir Igoshev [mailto:[log in to unmask]] Sent: Saturday, April 16, 2005 10:41 AM To: [log in to unmask]; Wenger, George M. Subject: Re: [TN] ENIG Gold Embrittlement George, I'm sorry but I'd like to "intervin e". Firsty, I think the "Black Pad" isn't exactly a case of brittle fracture (from the fracture mechanics point of view), and we know that "Brittle Fracture" is an another type of the problems ENIG is prone to. Secondly, in case of gold embrittement, the fracture path doesn't go along the intermetallic/Ni-P layer interface (at least from what I've seen and know). Regards, Vladimir. Sent from my Blackberry Wireless Vladimir Igoshev, 519-888-7465 ext.5283 -----Original Message----- From: TechNet <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Sent: Sat Apr 16 10:15:14 2005 Subject: Re: [TN] ENIG Gold Embrittlement Don, I interpret your question correctly, it sounds like you are asking if you can have "Gold Embrittlement". I believe you are asking the question because you have heard a lot of differing views concerning ENIG Black Pad brittle failures. One thing you shouldn't do is assume that a Black Pad failure is "Gold Embrittlement". There is a difference. As indicated in our ISTFA 2000 paper "Case Studies of Brittle Interfacial Failures in Area Array Solder Interconnects" one of the conclusions was "Two distinct Ni/Au embrittlement failure modes are verified. Embrittlement caused by formation of a secondary, Au-Sn intermetallic is fairly well understood. Embrittlement caused by poor electroless or immersion plating processes is not understood." I'll provide two answers to your question: Q1. Can you have "Gold Embrittlement" with ENIG A1. Yes if the ENIG solder joint has undergone long isothermal aging and the gold-tin IMC accumulates at an interface. Q2. Is a "Black Pad" brittle fracture due to "Gold Embrittlement" A2. No. The "Gold Embrittlement" caused by formation of a secondary gold-tin intermetallic has been evaluated for years and is fairly well understood. The "Black pad" brittle fractures are different and appear to be associated with the ENIG electroless and immersion plating processes and in my mind they are not well understood. My experience suggests that "Gold Embrittlement" happens when solder joints are made to electrolytic plated NiAu surface that have thick gold and "Black Pad" happens sometimes when solder joints are made to ENIG plated surfaces. The only similarity between these failures is that they brittle fractures at an interface. Regards, George George M. Wenger, Andrew Corporation Reliability / 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 Donald Kyle Sent: Saturday, April 16, 2005 9:32 AM To: [log in to unmask] Subject: [TN] ENIG Gold Embrittlement I have heard a lot of differing views about Gold Embrittlement lately here and I am curious, has anyone here found evidence that ENIG causes this? From what I have read, the ENIG process lays down about 120 to 240 micro inches of Ni and 2 to 4 micro inches of Au. If you calculate the percent by weight of Au in the solder joint, you have to have a very very thin stencil to even come close to having a problem with the Au. I have seen the following data from several different sources and most recently in a workshop presented by George Milad and Donald Gudeczauskas of Uyemura International Crop at APEX this past February. Their data shows that with a 5-mil stencil and a Au thickness of 20 micro inches, the percent of Au in the solder joint is 1.54%. Now of course, you are not going to get 20 micro inches out of this immersion process and even if you plated the Au, this is just at or below the threshold for Au embitterment. So with a nominal thickness of say 5-micro inches of Au and a 5-mil stencil, the percent by weight of Au in the solder joint would be 0.38%. Would this be a problem? I don't think so. So has anyone evidence that it does? Below are just two of many sites talking about gold embrittlement. These have some neat pictures to go along with the text. <http://www.npl.co.uk/ei/documents/gold.pdf>http://www.npl.co.uk/ei/docu ments/gold.pdf http://www.alphametals.com/products/solder_solutions/pdf/soldergld.pdf Donald Kyle C.I.D.+ 281-285-7528 voice 281-285-8593 fax [log in to unmask] Schlumberger Sugar Land Product Center (SPC) Mail Drop MD155-1 155 Industrial Boulevard Sugar Land, Texas 77478 --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- ------------------------------------------------------------------------ ------------------------ This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. 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