Julie,
How do you know it dewet from the substrate? I assume that the ball in question was soldered well (i.e., wet well with low contact angle) to the substrate and after the first reflow remained wet well to the substrate and also wet well to the PCB and then after the second reflow the ball was no longer attached to the substrate. Did the ball dewet from the substrate metallization? Did the substrate metallization dissolve into the solder? Or did the solder joint to the substrate fracture (i.e., broke and is no longer attached to the substrate?
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Thursday, June 30, 2011 6:10 PM
To: [log in to unmask]
Subject: Re: [TN] BGA ball dewet from substrate
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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