Hello Werner,

Regarding this issue, I just watched your video at IPC Midwest (which was just after Denny Fritz's interview about PERM).  Very interesting discussion.  Regarding the problem with SAC solder balls on BGA parts.  You expressed the concern (which I share) that because they won't supply them "ball-less", high performance applications that require tin-lead balls must first remove the SAC balls and then reball the packages and that process results in two temperature cycles which invalidates the part warranty.  You stated that you could not understand why parts vendors refuse to supply the parts without solder balls.  
 
I attended the 3rd PERM meeting this past week.  When the subject of BGA SAC solder balls and re-balling was raised, I suggested that perhaps the solution was not to re-ball but instead to dispense with the use of solder balls.  To use tin-lead solder paste to attach ball-less BGA parts to PC boards.  After all, I surmised, we attach QFN packages which have the same kind of pads that BGAs do. 
 
What do you think of this idea?  I realize there are a lot more pads on a BGA than a QFN but as more and more we go to BGA type packages to shrink the size of the package down to the size of the chips themselves, don't we need to re-think the use of solder balls?
 
Some at the meeting concurred with you and said that vendors refused to supply "ball-less" BGA packages.  
 
Some suggested that it was a requirement of the parts vendors for testing after packaging.  I replied that a test socket could be constructed which used pogo-pins or similar probing pins to make the temporary attachment for testing. 
 
Others were concerned about the mechanical stress that would result from eliminating the balls (as a stress relieving agent).  
 
Some agreed that the mechanical strength of the attachment would improve, that we would not see the voids that result with SAC solder balls
 
Some were concerned about the reduced clearance of the parts which would make the washing away of flux residue much more difficult.  My suggestion for that problem would be that perhaps the BGA packages have to have short pins that are gold plated instead of gold plated pads that then have solder balls attached.
 
It seems to me that a new package is needed now that the industry has had to transition to lead-free manufacturing.
 
I would be most interested in your comments on this idea.
 
Sincerely,

Bob Landman, President
Life Senior Member, IEEE
IEEE Power & Energy/Reliability Societies
IEEE Standards Association 
H&L Instruments, LLC
www.hlinstruments.com  
  

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Wednesday, October 07, 2009 3:38 PM
To: [log in to unmask]
Subject: Re: [LF] Quality/Reliability of 're-balled' BGA devices

 Hi Pete,
Other than the added cost and voiding the BGA warranties there is no down-side i have heard of.

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com


-----Original Message-----
From: Elmgren, Peter (GE EntSol, Security) <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Oct 7, 2009 10:36 am
Subject: [LF] Quality/Reliability of 're-balled' BGA devices

Anyone have any experience with the quality/reliability of 're-balled'
BGA devices?  Specifically, any experience with going from a lead-free BGA to a leaded BGA? 
 
Thanks,
 
Pete Elmgren 
GE Security, Inc.
 
(P) 941-308-8180
(C) 941-465-8991
 
www.gesecurity.com
8985 Town Center Parkway
Bradenton, Florida 34202
 

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