A question.
Which is screwed down first, the connector or the circuit board? If the board is first then extra strain will be on the joints when the connector is tightened.
Thanks,
Tim
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ricardo Moncaglieri
Sent: Wednesday, April 20, 2016 8:55 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Cracking After Thermal Cicling
Very precise each comment / suggestion. Thank you very much on each one of the received comments.
Matter has been put on my consideration as electronic service QA accountable just through these three pictures I´ve shared with all of you.
Provider development eng. dpmnt is not local they are abroad and our specific project manager had to travel in a rush due to this solder connection didnt pass the acceptance tests, then our project manager asked my opinion (I was not looking on such a trouble from the very
begining.....) my first considerations after doing several questions to them, were:
Might be a temperature test concern due to soldering aspect so as a CTE concern.
At that point of situation after several considerations we estimated necesary putting this matter under experts considerations: each one of you through technet forum.
Currently CTE of system behaviour is under reconsideration so as max.
temperature of tests.
As per last technet comments it has to go at the point otherwise it will be a waste of time.
On this line of thought it is a very good action to be taken into account the fact of modifying the mechanical connection between connector terminal and pcb pad stablishing of a proper strain relief. It should be done taking into account between other matters, the RF performance of the system.
Your expertise level and knowledge help a lot to us on focusing the troubleshooting process when we are against clock.
If any other consideration it will be welcome.
Just thank you very much, your support is unvaluable.
>>> "Stadem, Richard D." <[log in to unmask]> 20/04/2016 09:49
>>>
I totally agree with Ioan and Dave; you can do all of the analysis you want to see if there are soldering issues, plating issues, etc., but without a design change to eliminate or at least reduce the CTE stresses, you might be wasting your time.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Wednesday, April 20, 2016 7:41 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Cracking After Thermal Cicling
Ricardo,
In my opinion Dave's answer tells it all. You can spend more time testing for alloy composition, embrittlement and all the rest, but, if you want to make it work, there is an immediate action to take, the connector pins need to have compliance.
- Ideally the pins could be formed like the gullwing pins of ICs, but depending on the material of the pins and based on their rather large width, simply bending them might not help.
- Companies like http://www.sixsigmaservices.com/ or http://www.corfin.com/ can help you figuring out how to attach extensions to the pins, making them compliant.
- Best bet, change the design and replace the connector with one having compliant pins.
Good luck,
Ioan Tempea, P. Eng.
Manufacturing Engineer, Satellite Systems
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
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-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de David Hillman Envoyé
: Monday, April 18, 2016 8:25 PM À : [log in to unmask] Objet : 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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