Joe,
I did not see your note about test sockets not being an option. So here
is another method of temporary attachment.
If the pwb has holes in it for heatsink clamping onto the BGA, use them
to clamp a small aluminum bar across the top of the BGA. The process
goes like this:
        1. Start with a clean dry circuit board. Place the BGA
ball-side-down on a small       flat piece of tool steel and gently rub
back and forth while applying a light   pressure. This will create a
flat spot on the bottom of the solder balls. When       each solder ball
has a small flat spot you know they will all make contact with the
pwb pads later.
        2. Apply a very, very light coat of tacky flux to the pads to
help hold the BGA in    place. Do not get the flux outside of the BGA
body perimeter.
        3. Place the board into your rework machine, pick it up with the
vacuum, and align       the BGA to the pads and place it as if you were
going to do a rework. Use a nozzle      much smaller than the component
body. 
        4.Place the part onto its pads, but leave the nozzle down on the
part. Using ESD-        safe masking tape, tape the four sides of the
BGA down but leave the holes in the     PWB clear. 
        5. Lift the nozzle. Remove the board. Place the aluminum bar on
the top of the BGA      and gently tighten the screws/nuts to clamp the
BGA to the pads.
        6. X-ray to verify the alignment. Check the polarity as well.
        7. Gently wash the board to remove the flux. 
        8. Power up and see the cool blue sparks/corona/smoke under the
BGA (just kidding).

If the pwb does not have any mounting holes, epoxy two pemnuts to the
pwb on each side of the BGA pattern to use as screw retainers. Use SMT
epoxy, it can be gently chipped off after you are finished. You can heat
it up slightly for easier removal without any harm to the pwb.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Macko, Joe @ IEC
Sent: Thursday, July 20, 2006 12:16 PM
To: [log in to unmask]
Subject: [TN] temporary attachment of a BGA to a PCB for test

Fellow techs,



I have been asked to determine if there is a way to temporarily install
a BGA onto a test board using some type of conductive adhesive to make
electrical contact, electrical test and then safely remove the adhesive
without damaging the solder balls and be able to use the BGA.



Sounds impossible but I informed the design group I would check out the
options.



The other option we are looking at is to design a clamp/pallet that will
securely hold the BGA to the board.  The problem here may be making 100%
electrical contact on all 48 balls.



Anyone have any creative ideas they would like to share? Test sockets
are not an option.





thanks

Joe






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