No, that's when there's a non-wet. With head on pillow, the ball doesn't form a metallurgical bond to the solder paste. With this, the ball had a metallurgical joint to both substrate and PCB at one time, then de-wetted from the substrate during a subsequent reflow. Or at least that's the theory.
--------------------------------
Julie Silk
Environmental Compliance Technical Program Manager
Agilent Technologies
707-577-4296
[log in to unmask]
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: Thursday, June 30, 2011 3:06 PM
To: [log in to unmask]; SILK,JULIE (A-Sonoma,ex1)
Subject: Re: [TN] BGA ball dewet from substrate
Is it called head on pillow?
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Julie Silk [mailto:[log in to unmask]]
Sent: Thursday, June 30, 2011 06:05 PM
To: [log in to unmask] <[log in to unmask]>
Subject: [TN] BGA ball dewet from substrate
We have a failure analysis of "dewet" for a BGA ball that is separated from the component substrate. Does anyone know more about this failure mode? The part goes through reflow twice, so once while upside down. It seems unusual, even unlikely, for separation to occur between the balls and the substrate due to the weight of the part rather than between the ball and the PCB. Other parts on the same board do not have this issue. Do you have any experience with this problem or how to prevent it? Or for the future, how to predict it and thus avoid it? Would vapor phase processing influence the likelihood of this defect? Any help appreciated!
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