Hi Eric,

Of course anything that you can eliminate from the FA should be considered.

HOWEVER - since the failure is at the ball to substrate interface (I presume
you manufacture BGA's?) you would do far better to consider a side by side
comparison of the parameters of the shock tests (yours and theirs), and also
analysis of any unassembled BGA devices to analyze the metallurgy at the
ball to BGA substrate interface before the assembly sequence as well as the
same analysis on the failed units. For the record you will also need an
accurate assessment of the conditions at the solder joints during the
assembly reflow sequence as well as the details of the solder used for the
actual assembly.

John Burke

(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Monday, November 10, 2008 1:47 AM
To: [log in to unmask]
Subject: [TN] Effect of Soldering in a Ni atmosphere on BGA reliabilty

A customer has experienced solder joint failures in a lead free BGA 
device which are unexpected for us.

The test the solder joints failed was a shock test in the plane of the 
PWB and the joints failed at the interface between the SJ and our BGA 
device substrate.

We've done similar tests without failure but when we did our trials we 
soldered the devices onto the boards in a hot air oven. Our customer 
used a nitrogen oven. Could this affect SJ strength in any way?

Just wondering whether this is worth investigating.

Regards,


-- 
Eric Christison Msc
Mechanical Engineer
Consumer & Micro group
Imaging Division

STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom

Tel:	+44 (0)131 336 6165
Fax:	+ 44 (0)131 336 6001

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