Thanks Jerry,

Could you tell me why? I'm aware that BGA is favoured but can never come 
up with any killer reasons for not using LGA.

We use LGA because it results in a cheaper product which is more likely 
to result in a sale....and yes I expect you'll point out it's a false 
economy but people worry more about the $$s on a purchase order than the 
cost of rework (within reason).

Regards,



On 19/04/2011 16:52, Jerry Dengler wrote:
> 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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