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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