Hi John:
If there is a concern in damaging the balls or the SJ interface,
there should be a concern in damaging the pads and also crushing the
laminate and decreasing the distance between layers. Another approach
would be to support the BGA from the four sides and allowing the
pressure to be exerted on the sides of the BGA only. Making a fixture
where four thin long steel plates, one for each side, would be
positioned under the BGA sides to support it( there are other ways to
support the BGA). After which the heat sink is placed and pressed on the
BGA.
Just a thought.
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins
Sent: Thursday, February 02, 2006 7:15 PM
To: [log in to unmask]
Subject: Re: [TN] PSA heat sink attachment
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
The information contained in this electronic message is
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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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