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April 2016

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Guy Ramsey <[log in to unmask]>
Date:
Tue, 19 Apr 2016 09:39:35 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (405 lines)
Years ago a major supplier was participating in an FA training program at
our facility. During an EDS test of their solder sample we suspected the
alloy was incorrect. We later proved it, wrong melting point.
So, is it possible in this instance the solder was not 63/37?

On Tue, Apr 19, 2016 at 9:34 AM, Ricardo Moncaglieri <
[log in to unmask]> wrote:

> solder used: Sn63 Pb37
>
> >>> Ricardo Moncaglieri <[log in to unmask]> 19/04/2016 10:30
> >>>
> Resuming answers to several questions:
>
> At this time development engineers are reconsidering
> pcb-case-terminal-solder CTEs interaction.
> Laboratory eng reported test cycling temperature didnt pass in no case
> +125°C
>
> Both pictures are from the same specimen under test. Due too solder
> connection displacement when "cracking" in one of them you cann´t see
> the golden surface of terminal just at the left side.
>
> Degolding was done from double pre-tinned
>
> Thermal cycling is: 100 cycles -50°C to +125°C . Ramp rate per each
> cycle is 45´ (-50 to +125°C)
> (I´m sorry for correction, engineer test laboratory at first time
> reported +50°C to +125°C)
>
> brgds,Ricardo
>
> >>> George Wenger <[log in to unmask]> 19/04/2016 10:02 >>>
> It also won't hurt to do an XRF measurement on the PCB surface finish
> to know how thick the ImmAu and EPd were on the PCB
>
> ----- Original Message -----
>
> From: "David Hillman" <[log in to unmask]>
> To: [log in to unmask]
> Sent: Tuesday, April 19, 2016 8:31:22 AM
> 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 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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