These are lead-free BGAs.  Was lead-free solder used and if so, what type?

Bob Landman
H&L Instruments, LLC
www.hlinstruments.com
LDF Coatings, LLC
www.ldfcoatings.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Parsons
Sent: Friday, November 19, 2010 3:32 PM
To: [log in to unmask]
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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