We can do it John. That is what we do for leaving.
Vladimir

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

-----Original Message-----
From: John Parsons <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date:         Fri, 19 Nov 2010 13:17:07 
To: <[log in to unmask]>
Reply-To: [log in to unmask]
Subject: Re: [TN] BGA Falling off PCA

Thanks Werner for you input.  I had suspected that definitive answers might
only be obtained through SEM analysis and the like.  Can anyone recommend a
good lab?  We have used Microtek before but I don't think that they have an
SEM.

 

Regards

 

John

  _____  

From: Werner Engelmaier [mailto:[log in to unmask]] 
Sent: Friday, November 19, 2010 12:49 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] BGA Falling off PCA

 

Oh boy, John,
There are a number of possible root causes-also, remember that those BGAs
are the heaviest components and the thermally most massive ones. 
(1) this being ENIG, there is always 'Black Pad;'
(2) when soldering to ENIG, you are soldering to nickel-it is possible you
had an insufficient peak reflow temperature to cause adequate 'wetting' of
SAC solders to Ni;
(3) given SMD (solder mask defined) PCB pads, it could be a combination of
stress concentration and weak interface due to either 'Black Pad' or
insufficient reflow T's;
Full root cause determination will take cross-sections and SEM.
Werner

 

 

 

-----Original Message-----
From: John Parsons <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Nov 19, 2010 3:31 pm
Subject: [TN] BGA Falling off PCA

I am not seeing a lot of the usual Friday quiz traffic so I know you






 
guys-n-gals are just itching for some real work :o).






 







 
 






 







 
We are a PCB fabricator and one of our customers has returned some






 
assemblies to us for feedback.  What they noticed when someone accidentally






 
dropped an assembly is that the BGA (352 pin Cirrus Logic EP9312-CBZ) popped






 
off the board.  They then proceeded to drop a few more from a height of






 
about a foot with the same results.  All the other components on this






 
Pb-free assembly stay fast.  






 







 
 






 







 
We have received three PCA's and 5 BGA's.  On one of the BGA's a single ball






 
has remained on the PCB.  The rest of them all the balls have broken cleanly






 
from the PCB leaving a very flat (under x10 magnification) dull gray






 
surface.  I sure wish that I could take photo's but lighting is critical and






 
I don't think that I have the resources to get photo's that would do justice






 
to what the naked eye is seeing.






 







 
 






 







 
Also of note is that the BGA lands are mask defined with a 31mil circuit pad






 
and 26mil solder mask relief.






 







 
 






 







 
Does anyone have any ideas as to how we can determine the root cause of this






 
failure.  This part has been built for some time but previously the surface






 
finish on the PCB was a solder finish.  This is the first run of the boards






 
that has an ENIG finish.  This doesn't look to me like a raw board issue but






 
that is where everyone looks first isn't it ;o).






 







 
 






 







 
Regards






 







 
 






 







 
John Parsons






 







 
 






 







 







 







 
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