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September 2009

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Subject:
From:
Werner Engelmaier /* <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 4 Sep 2009 10:12:27 -0400
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text/plain
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Hi Joe,

In the '80's, we at Bell Labs tries round, and rectangular pads. The ATC results showd a slight reliability advantage for solder joints resulting from rectangular pads. I have a paper in SMI sometimes in the early '90's [Bell Labs management would not let it be published at the time] with the data. The reason for the rectangular pads , by the way, was smaller possible pitch.

Werner


-----Original Message-----
From: Joe Fjelstad <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, Sep 3, 2009 8:10 pm
Subject: [TN] BGA/LGA land shape versus assembly yield reliability




Greetings folks. 
 
I did a quick check of the archives on the subject and drilled a dry  well 
(maybe drilled in the wrong place?). 
 
That said, in design and lay out we all tend to match pad shapes on  the 
board with their mates on the package (round hole - round peg , square hole  - 
square peg)  
 
My question is has anyone looked at (or know of) round with square and  
vice versa and collected assembly efficacy/results and/or reliability  data? 
 
Finite Element Modeling data would be of interest as well.  
 
Thanks in advance for any responses
 
Joe
 
Since its Friday in some place of the world (or soon will be) I was looking 
 over the period table recently and afterwards was wondering if anyone  had 
ever mentioned that this little forum has it very own element,  TechNetium, 
the first man made element. (the upper case N is my  suggestion for future 
spelling... ;-)  

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