I do not know the "safe" load level.  This is likely dependent upon a lot of
factors with the ball pitch and ball/pad size being very important.  Another
major issue is keeping the board very flat during pressure application.  I
have seen the use of pneumatically "controlled" presses in assembly lines,
where the pressure went too high and the substrate fell from the board
leaving all the balls nicely attached to the PCB.  This was not a case of
ENIG black pad.  I would use the lowest possible pressure and make sure the
system elements are coplanar and well supported during load.


Best regards,
Leo

Leo M. Higgins III, Ph.D.
Vice President, Technical Support Operations
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704

office phone   512-383-4593
mobile           512-423-2002
[log in to unmask]
www.asat.com


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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John S. Berg
Sent: Wednesday, February 01, 2006 10:34 PM
To: [log in to unmask]
Subject: [TN] PSA heat sink attachment


We are attaching heat sinks to BGA's using a pressure sensitive adhesive
tape product. The recommended application pressures seem on the high side
based on some of our BGA part ball counts. Does anyone know the max safe
psi loading on a BGA ball/pad interface? The balls are eutectic and the
ball/pad interfaces are ENIG. Thanks in advance for help on this.

John Berg

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