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April 2011

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Subject:
From:
Dennis Fritz <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dennis Fritz <[log in to unmask]>
Date:
Tue, 19 Apr 2011 13:19:48 -0400
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text/plain (136 lines)
Seems to me from vibration and drop shock testing, that LGAs are less likely to fail than BGAs.   I know that BGAs in the current NASA/DoD round robin test were the first components to fail, but there were no comparable LGAs of the same size or I/O.  

Could it be the smaller mass because of the weight of the solder balls, or could it be less standoff from the board makes the LGA "stronger"?   

Any studies of the same device in BGA versus LGA through harsh environment - drop shock or vibration?

Denny Fritz
SAIC, Inc. 





-----Original Message-----
From: Stadem, Richard D. <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Tue, Apr 19, 2011 12:42 pm
Subject: Re: [TN] LGA geometry advice


LGAs are actually very trouble-free, but there are certain steps in the process 
hat need to be done to make them that way.
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Jerry Dengler
ent: Tuesday, April 19, 2011 10:52 AM
o: [log in to unmask]
ubject: Re: [TN] LGA geometry advice
Eric,
I would like to comment on the choice of LGA's.  These devices usually cause an 
ndue amount of trouble to manufacturing.  They are easily 3 times the trouble 
f a BGA.  I would rather do a .5 mm pitch BGA than a 1.0mm pitch LGA.
Regards,
Jerry Dengler
roduction Manager
ergamon Corporation
80 Crooked Lane, Unit# 3
ing of Prussia, PA  19406-2567
.S.A.
610) 239-0721 Phone
610) 239-0720 Fax
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Christison
ent: Tuesday, April 19, 2011 11:36 AM
o: [log in to unmask]
ubject: [TN] LGA geometry advice
Rights folks!
I'm designing a new surface mount device which originally started off as 
 X 5 square.
It has 25 I/Os.
It's LGA is a 5 X 5 array of 0.60 diameter pads on a 1 X 1 pitch.
The device has now increased in size to 7.5 X 7.5.
Now, do I increase the LGA spacing to cover the increased area again or 
o I stay with what fitted on the 5 X 5 device? I'm inclined to stick 
ith the original LGA as I believe that the stress analysis will tell me 
hat the smaller grid will have lower stresses in the SJs than the 
igger grid.
Are there any practical reasons for maximising grid size?
Regards,
-- 
ric Christison
onsumer&  Micro group
maging Division
STMicroelectronics (R&D) Ltd
3 Pinkhill
dinburgh EH12 7BF
nited Kingdom
Tel:	+44 (0)131 336 6165
ax:	+ 44 (0)131 336 6001
The contents of the email are ST confidential.


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