Hi Richard - Ricardo had mentioned the component leads were "double tinned"
to remove the gold but it sure wouldn't hurt to do a simple cross section
to confirm that gold embrittlement wasn't playing a role in the issue too.

Dave

On Tue, Apr 19, 2016 at 7:03 AM, Stadem, Richard D. <
[log in to unmask]> wrote:

> I agree with Dave, but with the addition that Steve may be on to something
> in that the "before" picture shows some gold, the "after" picture does not,
> so this may not be the same terminal. But that is irrelevant; what I am
> adding here is that the gold may be contributing to the issue as well, in
> the form of embrittlement.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Monday, April 18, 2016 7:25 PM
> To: [log in to unmask]
> Subject: Re: [TN] Solder Cracking After Thermal Cicling
>
> Hi folks - this case isn't as complicated as it might look. Its a simple
> case of CTE mismatch. The component lead is very very short with no strain
> relief bend. And as Joyce mentioned, the lead base metal may be
> accelerating the solder shear forces (i.e kovar or alloy 42). Add in the
> influences of the board laminate, the component body construction and the
> solder joint volume/pad size, you end up with the result shown in the
> photos.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Mon, Apr 18, 2016 at 5:05 PM, Ricardo Moncaglieri <
> [log in to unmask]> wrote:
>
> > Jim,
> > Temp cycle range is +50°C to +125°C.
> > I dont have yet the temp ramp rate.
> > brgds,Ricardo
> >
> > >>> "Maguire, James F" <[log in to unmask]> 18/04/2016 19:02
> > >>>
> > What is temp cycle condition again?  You have 50 to 125C but did you
> > mean -50C to +125C?  Also are you doing temp cycle or air/air temp
> > shock (ie. what is ramp rate in chamber or better yet as measured on
> > the product during temp cycle).
> >
> >
> > Jim Maguire
> > Intel Corporation
> > ATD Q&R Stress Lab Operations
> > Hawthorne Farms; Oregon
> > Engineer
> > Phone: 503-696-3309
> > Cell:  253-651-9373
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Ricardo
> > Moncaglieri
> > Sent: Monday, April 18, 2016 2:58 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Solder Cracking After Thermal Cicling
> >
> > Steve,
> > Responding your question.
> >
> > Soldered connection is not put under vibration during temp cicling.
> >
> > This terminal belongs to a connector which is screwed on a case and
> > its terminal passes through this metalic case and lyies on the pcb
> > ENEPIG pad.
> > So that there are following CTEs playing and intercating each other
> > all
> > together:
> >
> > PCB CTE
> > Solder CTE
> > Case CTE where is screwed the conector Terminal CTE
> >
> > brgds,Ricardo
> >
> > >>> Steve Gregory <[log in to unmask]> 18/04/2016 18:47 >>>
> > Hi Ricardo,
> >
> > I finally have your pictures up, they are here:
> >
> >
> > http://stevezeva.homestead.com/A15_Photos_of_pre__post_100_temp_cyclin
> > g_CSC-10_SN12.pdf
> >
> > Boy, that looks like a big CTE mis-match. A question; are the boards
> > going through ESS? Vibration along with the temp cycling?
> >
> > Steve
> >
> > On Mon, Apr 18, 2016 at 2:35 PM, Ricardo Moncaglieri <
> > [log in to unmask]> wrote:
> >
> > > Steve,
> > > Attached arethe pictures.
> > > Thank you a lot.
> > > Await for your comments.
> > > brgds,Ricardo
> > >
> > > >>> Steve Gregory <[log in to unmask]> 18/04/2016 15:22 >>>
> > > Hi Ricardo,
> > >
> > > The Technet server strips the attachments, send your photo directly
> > to me
> > > and I'll get it posted...
> > >
> > > Steve
> > >
> > > On Mon, Apr 18, 2016 at 11:43 AM, Ricardo Moncaglieri <
> > > [log in to unmask]> wrote:
> > >
> > > > Dear colleagues;
> > > >
> > > > Steve Gregory, could you please upload the enclosed picture?
> > > >
> > > > Solder become perturbated / cracked after thermal cicling:
> > > >
> > > > This picture corresponds to a plane (not circular) conector
> > terminal
> > > > solded to a pcb pad ENEPIG finished.
> > > > The connector terminal has been gold removed by twice pretin.
> > > > Solder used is Sn63Pb37.
> > > > Thermal cicling: 50°C to 125°C
> > > >
> > > > As picture showed there are stretch marks toward left direction
> > and
> > > > showed solder crack.
> > > >
> > > > Our provider reported temperature didnt pass over 125°C and solder
> > used
> > > > 63/37.
> > > >
> > > > Question:
> > > >
> > > > How could these kind of gooves or stretch marks have been produced
> >
> > > > taking into account they are just toward one direction (left) and
> > of
> > > > considerable length?
> > > > Just mecanic stress?
> > > > Temperature overpassing on any cicle?
> > > > Need of use of different alloy, ie.: In, Bi etc?
> > > > Provider reported the process is being useed from them since long
> > ago
> > > > (same solder alloy, temperature, pcb, terminal conector, thermal
> > > > cicling) but this is the first time they faced with such a
> > cracking.
> > > >
> > > > Do you have any comment in order to anlyse/solve this trouble.
> > > >
> > > > Appreciate your feedback we are in middle of a providing
> > acceptance
> > > > tests space quality level (IPC class 3).
> > > >
> > > > brgds,Ricardo
> > > >
> > > >
> > > >
> > > >
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