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May 2014

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Subject:
From:
"Wenger, George M. [Contractor]" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M. [Contractor]
Date:
Tue, 20 May 2014 14:48:01 -0500
Content-Type:
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text/plain (124 lines)
It looks like a brittle fracture at an IMC interface.

Regards,
George
George M. Wenger
Failure Signature & Characterization Lab LLC
609 Cokesbury Road, High Bridge, NJ 08829
(908) 638-8771 Home  (732) 309-8964 Mobile
E-mail [log in to unmask]
[log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, May 20, 2014 10:07 AM
To: [log in to unmask]
Subject: Re: [TN] Rif: RE: [TN] Rif: Re: [TN] pcb issue led to smt components drop from pcb

Hi Carmen!

Finally got your photos! I have them posted now. They are here:

http://stevezeva.homestead.com/1.jpg

http://stevezeva.homestead.com/7.jpg

So, is this happening on multiple boards? The same location on all boards? This looks pretty serious, I wouldn't trust the boards.
Definitely need a cross-section at a minimum to see what is going on...

Steve 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carmen Aloisi
Sent: Monday, May 19, 2014 7:17 AM
To: [log in to unmask]
Subject: [TN] Rif: RE: [TN] Rif: Re: [TN] pcb issue led to smt components drop from pcb

Hi Steve
here they are, these are the only kind of components that dop the other ones are well fixed on the pcba.
Thanks a lot,

Carmen



Hi Carmen!

Just reply to this email and I'll post your pictures....

Steve


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carmen Aloisi
Sent: Monday, May 19, 2014 12:58 AM
To: [log in to unmask]
Subject: [TN] Rif: Re: [TN] pcb issue led to smt components drop from pcb

Dear all
thanks a lot for your promt reply and suggestions, the pcbs have leaded hasl surface finishing I agree with you about potential intermetallic issues... fail pcbas are travelling right now from customer to our plant here in Italy and then I'll make some cross section.

I'd like to share pictures, how shall I contact mr Steve Gregory in order to post them?

Have a nice day
Carmen

Carmen Aloisi
Quality Manager

Eutron S.p.A.
Via Crespi 29 24020 Pradalunga (BG) Italy ph. +39 035697011 fax +39
035697090 m. +39 3355666074 www.eutron.com p.i. 01805190160




Hi Carmen-

You must get the surface analyzed.  I believe that it "looks like" bare exposed copper, but the odds are highly against that.  As Vladimir has suggested, you can hire an expert to do the whole analysis.  Or you can try to make this an educational journey for yourself.  If you get the surface analyzed, you'll need an analytical technique capable of identifying the various species and thicknesses of intermetallics which are on the metal surfaces.

Also, you need to understand the usage environment.  I believe that with the appropriate amount of temperature cycling, you can get the components to fall off of anything, provided there is a temperature or temperature coefficient of expansion difference between the component and substrate.

Looks like I might be the first to set off some tirades by mentioning "black pad".  This is a very ugly intermetallic which is associated with ENIG surface finish, and we providers of electronic assemblies spend many sleepless nights about it because you can have a beautiful joint which fails in even fairly mild usage environments.  Obviously we don't have enough information to suggest this as your problem, but it fits the final result (as do many other things!).

Shock will take off SMT components also, but that's usually a negligible probability (exceptions include crystals separating from cell phone motherboards when the cell phones are dropped or thrown).

Can you provide pictures?  We like to see pictures in TechNet.  You can't broadcast them directly, and we were using some kind of sharing site, but this guy named Steve Gregory takes pride in making it easy to send him pictures and he'll post them.  I think the "cc" address in this email is his current one, but he's changed companies a few times, so I'm not positive.
He seems to always watch for opportunities to help like this.

Once you post shots, all of the TechNet experts will come out of the woodwork with additional questions and arguments guaranteed to be somewhat amusing and possibly very educational.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carmen Aloisi
Sent: Friday, May 16, 2014 11:48 AM
To: [log in to unmask]
Subject: [TN] pcb issue led to smt components drop from pcb

Hello
I'm new to this forum and I'd like to address the following issue to the
group:
after 3 years from delivery of a batct of pcbas we got back from customer some of them  where components are dropping from the pcbas, the solder remains on the component pin and the pads are with exposed copper.
Could you help me in understanding what was wrong on pcb supplier process or on ours?

Thanks a lot in advance
Carmen Aloisi
Quality Manager

Eutron S.p.A.
Via Crespi 29 24020 Pradalunga (BG) Italy ph. +39 035697011 fax +39
035697090 m. +39 3355666074 www.eutron.com p.i. 01805190160


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