Michael, DC Folk

>With all the discussion with BGA assembly and rework,
>I was wondering if there is a reason why sockets are not
>more widely used for BGA's ? This would seem to solve maybe
>1/3 of the problems. The device wouldn't be
>subjected to the harsh removal and reball process and the
>board wouldn't have to be reworked as much.
>We're going to start using one for a 672 pin PBGA for this
>reason alone. We've had a few "alleged" defective
>devices and the $$ of the rework justified for at least
>trying the socket.

Sockets are great for prototyping, but can be an expensive
extra on a production board. BGA sockets aren't cheap, and
the manual work involved in fitting them and then loading
the chip is also not cheap. When you crunch the numbers
and think through all the tradeoffs it may not be the best
way for you to go - it really does depend on your situation.

If your failure rates are sufficiently high that sockets
become a cost effective option for BGA's then you may have
a serious problem with either your manufacturing process or
your design.

Also, from a layout perspective, the filthy great mounting
holes required for attaching the socket are just evil. :-)
Plus they restrict your use of rear mounted components
behind the BGA.

(Please note, my opinions are based on my experience with
the BGA sockets used at this company. Perhaps you have a
'friendlier' type of socket in mind, in which case the whole
tradeoff equation just changed.)

Regards

Brian Rusten

Senior PCB Design Engineer
Aristocrat Technologies Australia
85-113 Dunning Avenue
Rosebery NSW 2018 Australia
Tel:    +61 2 9697 4699
Fax:    +61 2 9663 1412
E-mail: [log in to unmask]


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