Hi Richard - well, we usually agree but not this time. The formation of the gold/tin IMC happens as the solder joint is molten and being formed. Gold and tin can form the IMC phase in a solid state condition but it is very very very slow and only in very rare occasions has been found to be a failure root cause. Gold will migrate and form gold/tin IMC in the presence of nickel plating but that is a Gibb's free energy issue and again, rarely is a failure root cause (think of all the ENIG boards soldered in the industry). If you don't have a gold embrittlement problem right after soldering, you have a very high probability of not having a gold embrittlement problem. The reason for all of the JSTD-001 criteria is an attempt to get folks to manage this issue proactively and not reactively. Dave On Wed, Nov 23, 2016 at 12:03 PM, Stadem, Richard D. < [log in to unmask]> wrote: > Just keep in mind that gold nucleation is a time-variable event. It begins > immediately after a solder joint is formed, but continues for a long time, > typically for two or three years or until equilibrium is reached. The > embrittlement due to gold nucleation will seldom be present immediately > after soldering, but solder joints will typically fail perhaps between 6 > months to two years later. > That is why the J-STD-001 reads that you must show objective proof, and > that proof needs to consider the time variable as a factor to test. > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir > Sent: Wednesday, November 23, 2016 11:27 AM > To: [log in to unmask] > Subject: Re: [TN] Gold embrittlement > > Hi Ioan, > > Au and Sn form intermetallic platelets and cracking goes at their > interface with the matrix. > > The fact that your product did pass the test doesn't mean there were no > cracking in solder and the product will last a as long as it supposed to in > field (it will depend on how good a reliability model was). > > I'd definitely suggest you to section joints after the test. > > Regards, > > Vladimir > > SENTEC > > Sent from my BlackBerry 10 smartphone on the Rogers network. > Original Message > From: Ioan Tempea > Sent: Wednesday, November 23, 2016 12:02 > To: [log in to unmask] > Reply To: TechNet E-Mail Forum > Subject: [TN] Gold embrittlement > > Dear Technos, > > I have SnPb37 joints with 4-8% Au that did not fail thermal cycling, no > cracks, pass electrical tests like a charm. This kinda contradicts > J-STD-001 and common knowledge, so I would appreciate some insider info > regarding Au embrittlement, to help me figure this one out. > > I know one could write volumes on this, but I'm sure the questions below > can be answered in a brief manner. > > > * How did Au embrittlement end up being a reliability issue? Real > catastrophic failures? > > * What is the effect on the long term reliability of solder joints? > > * What screening method creates catastrophic failure of embrittled joints > (mechanical shock, thermal cycling, vibration, etc.)? > > * It looks like the embrittlement process goes on as long as there's Au to > combine with Sn. What is the speed of this reaction? Otherwise said, how > long does it take for a joint with high Au content to become brittle? > > * Has anybody screen for embrittlement? Or, anyone tried to maximise > embrittlement (e.g. 100 hours @ 150 C) and then screened the hardware? > > * Anything else I should know? > > Thanks, > > Ioan Tempea, P. Eng. > Manufacturing Engineer, Satellite Systems > > [cid:[log in to unmask]] > > MacDonald, Dettwiler and Associates Corporation, 21025 Trans-Canada > Highway, Ste-Anne-de-Bellevue, QC, Canada H9X 3R2 > Tel: +1-514-457-2150 x3556 > www.mdacorporation.com<http://www.mdacorporation.com/> > > This e-mail, and any attachments, are intended solely for the use of the > intended recipient(s) and may contain legally privileged, proprietary > and/or confidential information. Any use, disclosure, dissemination, > distribution or copying of this e-mail and any attachments for any purposes > that have not been specifically authorized by the sender is strictly > prohibited. If you are not the intended recipient, please immediately > notify the sender by reply e-mail and permanently delete all copies and > attachments. This email is for informational purposes only and shall not be > interpreted to authorize or conclude a binding agreement between MDA and > any other party unless this email contains or is accompanied by an express > written confirmation of MDA's intention to enter into a binding agreement, > such confirmation shall only be provided by an authorized representative of > MDA. >