Hi Vlad - we encountered the "trench etch" defect during the NASA DoD
consortia effort. Take a look under the PDIP section of this report for
the specific FA analysis:
https://tdksc.ksc.nasa.gov/servlet/dm.web.Fetch/TEERMRockwell_Collins_-55C_to__125C_Thermal_Cycle_Testing.pdf?gid=142260&FixForIE=TEERMRockwell_Collins_-55C_to__125C_Thermal_Cycle_Testing.pdf
We essentially had a case of a plating defect in combination with
lead-free soldering on an immersion silver finish. Apparently this anomaly
happens on occasion within the industry but it was the first time I had
seen it after using ImAg surface finishes for over 12 years.
Dave
From: Vladimir Igoshev <[log in to unmask]>
To: <[log in to unmask]>
Date: 03/04/2013 08:41 AM
Subject: Re: [TN] Conductive path failure in thermal cycling
Sent by: TechNet <[log in to unmask]>
Hi Dave,
Can you share an image of the defect?
Regards,
Vladimir
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (647) 495-8727
Cell: (416) 899-1882
www.sentec.ca
-----Original Message-----
From: "David D. Hillman" <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Mon, 4 Mar 2013 08:08:34
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
<[log in to unmask]>
Subject: Re: [TN] Conductive path failure in thermal cycling
Hi Ioan - I have recently ran into an plating process issue with immersion
silver - the term being used to describe the anomaly is "trench etch".
This defect is made worst by lead-free soldering processes where copper
dissolution comes into play. Your defect sounds like it could be "trench
etch" but you have ENIG and not immersion silver. Please send Steve a
couple of pictures of your defect and we'll try to sleuth out the root
cause.
Dave
From: Ioan Tempea <[log in to unmask]>
To: <[log in to unmask]>
Date: 03/01/2013 03:08 PM
Subject: Re: [TN] Conductive path failure in thermal cycling
Sent by: TechNet <[log in to unmask]>
ENIG
Ioan Tempea, ing.
Ingénieur principal de fabrication / Senior Manufacturing Engineer
[signature002]<http://www.digico.cc/>
950 RUE BERGAR, LAVAL, QC, H7L 5A1<http://g.co/maps/2gh3f>
T+ 1 (450) 967-7100, EXT244
------------------------------------------------------------------------
[signature001] <http://www.facebook.com/pages/Digico/277076778479>
------------------------------------------------------------------------
Lauréat Dunamis 2012<http://digico.cc/dunamis-2012/>
Entreprise manufacturière / Gestion du capital humain
De : [log in to unmask] [mailto:[log in to unmask]]
Envoyé : March-01-13 2:30 PM
À : TechNet E-Mail Forum; Ioan Tempea
Objet : Re: [TN] Conductive path failure in thermal cycling
Hi Ioan - what is the assembly surface finish?
Dave Hillman
Rockwell Collins
[log in to unmask]<mailto:[log in to unmask]>
From: Ioan Tempea <[log in to unmask]<mailto:[log in to unmask]>>
To: <[log in to unmask]<mailto:[log in to unmask]>>
Date: 03/01/2013 10:40 AM
Subject: [TN] Conductive path failure in thermal cycling
Sent by: TechNet <[log in to unmask]<mailto:[log in to unmask]>>
________________________________
Dear Technos,
RoHS assembly, soldered with SAC305 alloy, 0.075" thick 14 layers PCB,
failing after 250 cycles (-20 C to 125 C).
Failure mode is crack between the traces and pad at 3 places. Happens on 2
TH components. Traces are 0.0055" wide, pads are 0.022" in diameter on the
via side or 0.065" on the component side. There is no tear dropping.
Should I bother figuring out if manual soldering of the TH component
fragilizes the trace-pad junction, or this is an obvious case of design
induced failure?
Thanks,
Ioan Tempea, ing.
Ingénieur principal de fabrication / Senior Manufacturing Engineer
[signature002]<http://www.digico.cc/>
950 RUE BERGAR, LAVAL, QC, H7L 5A1<http://g.co/maps/2gh3f>
T+ 1 (450) 967-7100, EXT244
------------------------------------------------------------------------
[signature001] <http://www.facebook.com/pages/Digico/277076778479>
------------------------------------------------------------------------
Lauréat Dunamis 2012<http://digico.cc/dunamis-2012/>
Entreprise manufacturière / Gestion du capital humain
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