TECHNET Archives

April 2016

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
George Wenger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 19 Apr 2016 21:41:56 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (271 lines)
Ricardo, 

The other reason for doing a cross section is to see what is happening at the lead/solder/PCB interface. I'm trying to find my copy of the old NCMS PCB Surface Finishes five year project but I'm pretty sure it was determined that Palladium does not form a strong intermetallic bond with lead in Sn/Pb solders and when there is a CTE mismatch you can certainly have what your photos seem to indicate. That is one of the reasons I suggested doing XRF measurements of the gold on the leads and immersion Au and electroless Pd 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 
> > > > 
> > > > 
> > > > 
> > > > 
> > ______________________________________________________________________ 
> > > > This email has been scanned by the Symantec Email Security.cloud 
> > service. 
> > > > For more information please contact helpdesk at x2960 or 
> > > [log in to unmask] 
> > > > 
> > ______________________________________________________________________ 
> > > > 
> > > 
> > > -- 
> > > 
> > > 
> > > This email and any attachments are only for use by the intended 
> > > recipient(s) and may contain legally privileged, confidential, 
> > proprietary 
> > > or otherwise private information. Any unauthorized use, 
> > reproduction, 
> > > dissemination, distribution or other disclosure of the contents of 
> > this 
> > > e-mail or its attachments is strictly prohibited. If you have 
> > received 
> > > this 
> > > email in error, please notify the sender immediately and delete the 
> > > original. 
> > > 
> > > 
> > ______________________________________________________________________ 
> > > This email has been scanned by the Symantec Email Security.cloud 
> > service. 
> > > For more information please contact helpdesk at x2960 or 
> > [log in to unmask] 
> > > 
> > ______________________________________________________________________ 
> > > 
> > 
> > 
> > ______________________________________________________________________ 
> > This email has been scanned by the Symantec Email Security.cloud 
> > service. 
> > For more information please contact helpdesk at x2960 or 
> > [log in to unmask] 
> > ______________________________________________________________________ 
> > 
> > ______________________________________________________________________ 
> > This email has been scanned by the Symantec Email Security.cloud service. 
> > For more information please contact helpdesk at x2960 or 
> > [log in to unmask] 
> > ______________________________________________________________________ 
> > -- 
> > 
> > 
> > This email and any attachments are only for use by the intended 
> > recipient(s) and may contain legally privileged, confidential, 
> > proprietary or otherwise private information. Any unauthorized use, 
> > reproduction, dissemination, distribution or other disclosure of the 
> > contents of this 
> > 
> > e-mail or its attachments is strictly prohibited. If you have received 
> > this email in error, please notify the sender immediately and delete 
> > the original. 
> > 
> > ______________________________________________________________________ 
> > This email has been scanned by the Symantec Email Security.cloud 
> > service. 
> > For more information please contact helpdesk at x2960 or 
> > [log in to unmask] 
> > ______________________________________________________________________ 
> > 
> > ______________________________________________________________________ 
> > This email has been scanned by the Symantec Email Security.cloud 
> > service. 
> > For more information please contact helpdesk at x2960 or 
> > [log in to unmask] 
> > ______________________________________________________________________ 
> > 
> 
> ______________________________________________________________________ 
> This email has been scanned by the Symantec Email Security.cloud service. 
> For more information please contact helpdesk at x2960 or [log in to unmask] 
> ______________________________________________________________________ 
> 

______________________________________________________________________ 
This email has been scanned by the Symantec Email Security.cloud service. 
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________ 


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2