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April 2011

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Subject:
From:
Jerry Dengler <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jerry Dengler <[log in to unmask]>
Date:
Tue, 19 Apr 2011 11:52:23 -0400
Content-Type:
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Eric,

I would like to comment on the choice of LGA's.  These devices usually cause an undue amount of trouble to manufacturing.  They are easily 3 times the trouble of a BGA.  I would rather do a .5 mm pitch BGA than a 1.0mm pitch LGA.

Regards,

Jerry Dengler
Production Manager
Pergamon Corporation
380 Crooked Lane, Unit# 3
King of Prussia, PA  19406-2567
U.S.A.
(610) 239-0721 Phone
(610) 239-0720 Fax

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Christison
Sent: Tuesday, April 19, 2011 11:36 AM
To: [log in to unmask]
Subject: [TN] LGA geometry advice

Rights folks!

I'm designing a new surface mount device which originally started off as 
5 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 
do I stay with what fitted on the 5 X 5 device? I'm inclined to stick 
with the original LGA as I believe that the stress analysis will tell me 
that the smaller grid will have lower stresses in the SJs than the 
bigger grid.

Are there any practical reasons for maximising grid size?

Regards,

-- 
Eric Christison
Consumer&  Micro group
Imaging Division

STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom

Tel:	+44 (0)131 336 6165
Fax:	+ 44 (0)131 336 6001

The contents of the email are ST confidential.




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