IMHO:
I my examination of the three photos I see two artifacts that repeat in each photo. Perhaps the angle and mag has changed.
In photo 2 there is a small reflective objects where the three arrows intersect. This same object is on all three photos.
In photo 2 directly north of the middle arrow there is a depression which is also on all three photos.
My two cents worth.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Tuesday, April 19, 2016 7:31 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Cracking After Thermal Cicling
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 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 don't have yet the temp ramp rate.
> > brgds,Ricardo
> >
> > >>> "Maguire, James F" 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 cycling.
> >
> > This terminal belongs to a connector which is screwed on a case and
> > its terminal passes through this metallic case and lyies on the pcb
> > ENEPIG pad.
> > So that there are following CTEs playing and interacting each other
> > all
> > together:
> >
> > PCB CTE
> > Solder CTE
> > Case CTE where is screwed the connector Terminal CTE
> >
> > brgds,Ricardo
> >
> > >>> Steve Gregory 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_cycl
> > in
> > 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 are the pictures.
> > > Thank you a lot.
> > > Await for your comments.
> > > brgds,Ricardo
> > >
> > > >>> Steve Gregory 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 cycling:
> > > >
> > > > This picture corresponds to a plane (not circular) connector
> > terminal
> > > > scolded to a pcb pad ENEPIG finished.
> > > > The connector terminal has been gold removed by twice pretin.
> > > > Solder used is Sn63Pb37.
> > > > Thermal cycling: 50°C to 125°C
> > > >
> > > > As picture showed there are stretch marks toward left direction
> > and
> > > > showed solder crack.
> > > >
> > > > Our provider reported temperature didn't 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 cycle?
> > > > Need of use of different alloy, ie.: In, Bi etc?
> > > > Provider reported the process is being used from them since
> > > > long
> > ago
> > > > (same solder alloy, temperature, pcb, terminal connector, thermal
> > > > cycling) but this is the first time they faced with such a
> > cracking.
> > > >
> > > > Do you have any comment in order to analyze/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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